TopGit - A different patch queue manager
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Signed-off-by: Adam Mizerski <adam@mizerski.pl>
Signed-off-by: Kyle J. McKay <mackyle@gmail.com>
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tg-next.sh tg: previous to next overhaul Mar 31, 2017
tg-patch.sh tg: reduce subshell creation phase III Feb 21, 2018
tg-prev.sh tg: previous to next overhaul Mar 31, 2017
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tg-shell.sh tg: add wayback machine Jun 26, 2017
tg-summary.sh tg-summary.sh: restore correct -i and -w operation Mar 4, 2018
tg-tag.sh tg-tag.sh: remove shell-confusing, unnecessary space Mar 21, 2018
tg-update.sh tg: avoid passing '--' options terminator to git cat-file Apr 26, 2018
tg.sh tg.sh: next version is 0.19.13 Jan 10, 2019

README.rst

TopGit -- A different patch queue manager

DESCRIPTION

TopGit aims to make handling of large amounts of interdependent topic branches easier. In fact, it is designed especially for the case where you maintain a queue of third-party patches on top of another (perhaps Git-controlled) project and want to easily organize, maintain and submit them -- TopGit achieves that by keeping a separate topic branch for each patch and providing some tools to maintain the branches.

See also:

REQUIREMENTS:Installation requirements
SYNOPSIS:Command line example session
USAGE:Command line details
NO UNDO:Where's the undo!!!
CONVENTIONS:Suggestions for organizing your TopGit branches
EXTRA SETTINGS:Various possible "topgit.*" config settings
ALIASES:Git-like TopGit command aliases
NAVIGATION:Getting around with "next" and "prev"
WAYBACK MACHINE:Turn back the clock and then come back
GLOSSARY:All the TopGit vocabulary in one place
TECHNICAL:How it works behind the scenes
TESTING TOPGIT:How to run the TopGit test suite

REQUIREMENTS

TopGit is a collection of POSIX shell scripts so a POSIX-compliant shell is required along with some standard POSIX-compliant utilities (e.g. sed, awk, cat, etc.). Git version 1.9.2 or later is also required.

To use TopGit with linked working trees (the git worktree add command), at least Git version 2.5.0 (obviously, since that's when the git worktree command first appeared) is needed in which case linked working trees are then fully supported for use with TopGit.

The scripts need to be preprocessed and installed. The Makefile that does this requires a POSIX make utility (using "make" and "make install") and some version of perl in the PATH somewhere (the perl binary is needed for correct help text file generation prior to the actual install).

Once installed, TopGit uses only POSIX-compliant utilities (except that it also requires, obviously, Git).

Running the tests (see TESTING TOPGIT) has the same requirements as for installation (i.e. POSIX plus Perl).

It is possible to use the DESTDIR functionality to install TopGit to a staging area on one machine, archive that and then unarchive it on another machine to perform an install (provided the build prefix and other options are compatible with the final installed location).

INSTALLATION

See the file INSTALL.

GIT REPOSITORY

The TopGit git repository can be found at <http://repo.or.cz/topgit/pro>.

RATIONALE

Why not use something like StGIT or Guilt or rebase -i for maintaining your patch queue? The advantage of these tools is their simplicity; they work with patch series and defer to the reflog facility for version control of patches (reordering of patches is not version-controlled at all). But there are several disadvantages -- for one, these tools (especially StGIT) do not actually fit well with plain Git at all: it is basically impossible to take advantage of the index effectively when using StGIT. But more importantly, these tools horribly fail in the face of a distributed environment.

TopGit has been designed around three main tenets:

(i) TopGit is as thin a layer on top of Git as possible. You still maintain your index and commit using Git; TopGit will only automate a few indispensable tasks.

(ii) TopGit is anxious about keeping your history. It will never rewrite your history, and all metadata is also tracked by Git, smoothly and non-obnoxiously. It is good to have a single point when the history is cleaned up, and that is at the point of inclusion in the upstream project; locally, you can see how your patch has evolved and easily return to older versions.

(iii) TopGit is specifically designed to work in a distributed environment. You can have several instances of TopGit-aware repositories and smoothly keep them all up-to-date and transfer your changes between them.

As mentioned above, the main intended use-case for TopGit is tracking third-party patches, where each patch is effectively a single topic branch. In order to flexibly accommodate even complex scenarios when you track many patches where many are independent but some depend on others, TopGit ignores the ancient Quilt heritage of patch series and instead allows the patches to freely form graphs (DAGs just like Git history itself, only "one level higher"). For now, you have to manually specify which patches the current one depends on, but TopGit might help you with that in the future in a darcs-like fashion.

A glossary plug: The union (i.e. merge) of patch dependencies is called a base of the patch (topic branch).

Of course, TopGit is perhaps not the right tool for you:

(i) TopGit is not complicated, but StGIT et al. are somewhat simpler, conceptually. If you just want to make a linear purely-local patch queue, deferring to StGIT instead might make more sense.

(ii) When using TopGit, your history can get a little hairy over time, especially with all the merges rippling through. ;-)

SYNOPSIS

## Create and evolve a topic branch
$ tg create t/gitweb/pathinfo-action
tg: Automatically marking dependency on master
tg: Creating t/gitweb/pathinfo-action base from master...
$ ..hack..
$ git commit
$ ..fix a mistake..
$ git commit

## Create another topic branch on top of the former one
$ tg create t/gitweb/nifty-links
tg: Automatically marking dependency on t/gitweb/pathinfo-action
tg: Creating t/gitweb/nifty-links base from t/gitweb/pathinfo-action...
$ ..hack..
$ git commit

## Create another topic branch on top of master and submit
## the resulting patch upstream
$ tg create t/revlist/author-fixed master
tg: Creating t/revlist/author-fixed base from master...
$ ..hack..
$ git commit
$ tg patch -m
tg: Sent t/revlist/author-fixed
From: pasky@suse.cz
To: git@vger.kernel.org
Cc: gitster@pobox.com
Subject: [PATCH] Fix broken revlist --author when --fixed-string

## Create another topic branch depending on two others non-trivially
$ tg create t/whatever t/revlist/author-fixed t/gitweb/nifty-links
tg: Creating t/whatever base from t/revlist/author-fixed...
tg: Merging t/whatever base with t/gitweb/nifty-links...
Merge failed!
tg: Please commit merge resolution and call: tg update --continue
tg: It is also safe to abort this operation using `git reset --hard`
tg: but please remember you are on the base branch now;
tg: you will want to switch to a different branch.
$ ..resolve..
$ git commit
$ tg update --continue
$ ..hack..
$ git commit

## Update a single topic branch and propagate the changes to
## a different one
$ git checkout t/gitweb/nifty-links
$ ..hack..
$ git commit
$ git checkout t/whatever
$ tg info
Topic Branch: t/whatever (1 commit)
Subject: [PATCH] Whatever patch
Base: 3f47ebc1
Depends: t/revlist/author-fixed t/gitweb/nifty-links
Needs update from:
        t/gitweb/nifty-links (1 commit)
$ tg update
tg: Updating base with t/gitweb/nifty-links changes...
Merge failed!
tg: Please commit merge resolution and call `tg update --continue`
tg: (use `tg status` to see more options)
$ ..resolve..
$ git commit
$ tg update --continue
tg: Updating t/whatever against new base...
Merge failed!
tg: Please commit merge resolution and call `tg update --continue`
tg: (use `tg status` to see more options)
$ ..resolve..
$ git commit
$ tg update --continue

## Update a single topic branch and propagate the changes
## further through the dependency chain
$ git checkout t/gitweb/pathinfo-action
$ ..hack..
$ git commit
$ git checkout t/whatever
$ tg info
Topic Branch: t/whatever (1/2 commits)
Subject: [PATCH] Whatever patch
Base: 0ab2c9b3
Depends: t/revlist/author-fixed t/gitweb/nifty-links
Needs update from:
        t/gitweb/pathinfo-action (<= t/gitweb/nifty-links) (1 commit)
$ tg update
tg: Recursing to t/gitweb/nifty-links...
[t/gitweb/nifty-links] tg: Updating base with t/gitweb/pathinfo-action changes...
Merge failed!
[t/gitweb/nifty-links] tg: Please commit merge resolution and call `tg update --continue`
[t/gitweb/nifty-links] tg: (use `tg status` to see more options)
$ ..resolve..
$ git commit
$ tg update --continue
[t/gitweb/nifty-links] tg: Updating t/gitweb/nifty-links against new base...
Merge failed!
[t/gitweb/nifty-links] tg: Please commit merge resolution and call `tg update --continue`
[t/gitweb/nifty-links] tg: (use `tg status` to see more options)
$ ..resolve..
$ git commit
$ tg update --continue
tg: Updating base with t/gitweb/nifty-links changes...
tg: Updating t/whatever against new base...

## Clone a TopGit-controlled repository
$ git clone URL repo
$ cd repo
$ tg remote --populate origin
...
$ git fetch
$ tg update

## Add a TopGit remote to a repository and push to it
$ git remote add foo URL
$ tg remote foo
$ tg push -r foo

## Update from a non-default TopGit remote
$ git fetch foo
$ tg -r foo summary
$ tg -r foo update

CONVENTIONS

When using TopGit there are several common conventions used when working with TopGit branches. None of them are enforced, they are only suggestions.

There are three typical uses for a TopGit branch:

  1. [PATCH] Normal TopGit branches that represent a single patch. These are known as "patch" TopGit branches.
  2. [BASE] Empty TopGit branches with no dependencies (an empty .topdeps file) that represent a base upon which other "normal" TopGit branches depend. These are known as "base" TopGit branches (not to be confused with the refs/top-bases/... refs).
  3. [STAGE] Empty TopGit branches that serve as a staging area to bring together several other TopGit branches into one place so they can be used/tested all together. These are known as "stage" TopGit branches.

An "empty" TopGit branch is one that does not have any changes of its own -- it may still have dependencies though ("stage" branches do, "base" branches do not). The tg summary output shows empty branches with a 0 in the listing. Normal "patch" branches that have not been annihilated, "base" and "stage" branches fall into this category. (Annihilated branches are normally omitted from the tg summary output but can be shown if given explicitly as an argument to the tg summary command. However, the message line will be incorrect since an annihilated branch has no .topmsg file of its own.)

A "patch" branch name typically starts with t/ whereas "base" and "stage" branch names often do not.

A "base" branch is created by using the --base option of tg create (aka --no-deps) which will automatically suggest a "[BASE]" message prefix rather than "[PATCH]". A "stage" branch is created like a normal patch branch except that the only changes that will ever be made to it are typically to add/remove dependencies. Its subject prefix must be manually changed to "[STAGE]" to reflect its purpose.

Since both "base" and "stage" branches typically only have a use for the "Subject:" line from their .topmsg file, they are quite easily created using the --topmsg option of tg create.

Use of "stage" and "base" branches is completely optional. However, without use of a "stage" branch it will be difficult to test multiple independent patches together all at once. A "base" branch is merely a convenience that provides more explicit control over when a common base for a set of patches gets updated as well as providing a branch that shows in tg summary output and participates in tg remote --populate setup.

Occasionally the functionality of a "base" branch is needed but it may not be possible to add any .topdeps or .topmsg files to the desired branch (perhaps it's externally controlled). BARE BRANCHES can be used in this case, but while TopGit allows them it deliberately does not provide assistance in setting them up.

Another advantage to using a "stage" branch is that if a new "patch" branch is created remotely and that new branch is added to a pre-existing "stage" branch on the remote then when the local version of the "stage" branch is updated (after fetching remote updates of course), that new dependency will be merged into the local "stage" branch and the local version of the new remote "patch" branch will be automatically set up at "tg update" time.

When using the tg tag command to create tags that record the current state of one or more TopGit branches, the tags are often created with a name that starts with t/.

One last thing, you have enabled git rerere haven't you?

NO UNDO

Beware, there is no "undo" after running a tg update!

Well, that's not entirely correct. Since tg update never discards commits an "undo" operation is technically feasible provided the old values of all the refs that were affected by the tg update operation can be determined and then they are simply changed back to their previous values.

In practice though, it can be extremely tedious and error prone looking through log information to try and determine what the correct previous values were. Although, since TopGit tries to make sure reflogs are enabled for top-bases refs, using Git's @{date} notation on all the refs dumped out by a tg tag --refs foo, where "foo" is the branch that was updated whose update needs to be undone, may work.

Alternatively, tg tag --stash can be used prior to the update and then tg revert used after the update to restore the previous state. This assumes, of course, that you remember to run tg tag --stash first.

The tg update command understands a --stash option that tells it to automatically run tg tag --stash before it starts making changes (if everything is up-to-date it won't run the stash command at all).

The --stash option is the default nowadays when running tg update, add the --no-stash option to turn it off.

There is a preference for this. Setting the config value topgit.autostash to false will implicitly add the --no-stash option to any tg update command unless an explicit --stash option is given.

If you are likely to ever want to undo a tg update, setting topgit.autostash to false is highly discouraged!

Note that if you have foolishly disabled the autostash functionality and suddenly find yourself in an emergency "WHERE'S THE UNDO???" situation you may be able to use the special TG_STASH ref. But only if you're quick. It's only set if you've foolishly disabled autostash and it always overwrites the previous TG_STASH value if there was one (there's no reflog for it) and it will most likely not survive a git gc (even an automatic one) no matter what gc expiration values are used. However, as a last gasp attempt to save your butt, a previously existing TG_STASH will first be renamed to ORIG_TG_STASH immediately before a new TG_STASH gets written (stepping on any previously existing ORIG_TG_STASH at that point).

Note that the tags saved by tg tag --stash are stored in the refs/tgstash ref and its reflog. Unfortunately, while Git is happy to maintain the reflog (once it's been enabled which tg tag guarantees for refs/tgstash), Git is unable to view an annotated/signed tag's reflog! Instead Git dereferences the tag and shows the wrong thing.

Use the tg tag -g command to view the refs/tgstash reflog instead.

WAYBACK MACHINE

After reading about NO UNDO and the tg tag command used to provide a semblance of undo in some cases, you have the foundation to understand the wayback machine.

The "wayback machine" provides a way to go back to a previous ref state as stored in a TopGit tag created by tg tag. It actually normally returns to a hybrid state as it does not prune (unless you prefix the wayback tag with a :). In other words, any refs that have been newly created since the target tag was made will continue to exist in the "wayback" view of things (unless you used a pruning wayback tag -- one prefixed with a :).

Any operations that are read-only and do not require working tree files (e.g. the -i or -w options of tg patch) are allowed using the wayback machine. Simply add a global -w <tgtag> option to the command.

This functionality can be extremely useful for quickly examining/querying a previous state recorded some time ago with a tg tag.

As the wayback machine uses a separate caching area, expect initial operations to be less speedy, but repeated wayback operations on the same wayback tag should happen at normal speed.

One new command exists expressly for use with the wayback machine.

The tg shell command will spawn an interactive shell or run a specific shell command in a temporary writable and non-bare repository that has its ref namespace set to the (possibly pruned if it's a pruning wayback tag) wayback tag's view of the world. This pretty much lifts all wayback restrictions, but read the description for tg shell for more details. There is an option available to specify the location where this "temporary" directory is created thereby allowing it to persist, but the same warnings then apply as using the git clone --shared command.

EXTRA SETTINGS

TopGit supports various config settings:

tg create:format.signoff template Signed-off-by line
ALIASES:topgit.alias.* for Git-like command aliases
tg update:topgit.autostash automatic stash control
tg create:topgit.bcc default "Bcc:" value for create
tg create:topgit.cc default "Cc:" value for create
tg patch:topgit.from "From:" fixups by tg patch
tg push:topgit.pushRemote default push remote
REMOTE HANDLING:topgit.remote TopGit's default remote
SEQUESTRATION:topgit.sequester for sequestration control
tg update:topgit.setAutoUpdate => rerere.autoUpdate
tg export:topgit.subjectMode export [...] tag removal
tg create:topgit.subjectPrefix "[$prefix PATCH] foo"
tg create:topgit.to default "To:" value for create
tg migrate-bases:topgit.top-bases for refs bases location

ALIASES

These work exactly like Git's aliases except they are stored under topgit.alias.* instead. See the git help config output under the alias.* section for details. Do note that while alias nesting is explicitly permitted, a maximum nesting depth of 10 is enforced to help detect accidental aliasing loops and keep them from wedging the machine.

For example, to create an lc alias for the tg log --compact command this command may be used:

git config --global topgit.alias.lc "log --compact"

To make it specific to a particular repository just omit the --global option from the command.

NAVIGATION

From Previous to Next

For this section, consider the following patch series, to be applied in numerical order as shown:

0001-F_first-patch.diff
0002-G_second-builds-on-F.diff
0003-H_third-builds-on-G.diff
0004-I_fourth-builds-on-H.diff
0005-J_fifth-builds-on-I.diff
0006-K_sixth-builds-on-J.diff
0007-L_last-patch-needs-K.diff

If these were applied to some commit in a Git repository, say commit "A" then a history that looks like this would be created:

A---F---G---H---I---J---K---L

Where the parent of commit "F" is "A" and so on to where the parent of commit "L" is commit "K".

If that commit history, from A through L, was then imported into TopGit, one TopGit branch would be created corresponding to each of the commits F through L. This way, for example, if the fourth patch in the series (0004-I_...diff) needs work, the TopGit branch corresponding to its patch can be checked out and changes made and then a new version of its patch created (using tg patch) without disturbing the other patches in the series and when tg update is run, the patches that "follow" the fourth patch (i.e. 5, 6 and 7) will have their corresponding TopGit branches automatically updated to take into account the changes made to the fourth patch.

Okay, enough with the review of TopGit systemology

Imagine then that you are working on the fourth patch (i.e. you have its branch checked out into the working tree) and you want to move to the following patch in the series because you have a nit to pick with it too.

If you can't remember the exact name you might have to fumble around or, you can display the name of the following or "next" patch's branch with the, you guessed it, tg next command. Think of "next" as the "next" logical patch in the series or the next following patch. If the patches are numbered as in the list above, "next" corresponds to the "+1" (plus one) patch.

You might have already guessed there's a corresponding tg prev command which displays the "-1" (minus one) patch. If these commands (tg next and tg prev) are not given a branch name to start at they start at the patch corresponding to the current HEAD.

Displaying, however, is not so helpful as actually going there. That's where the tg checkout command comes in. tg checkout next does a git checkout of the tg next branch and, not surprisingly, tg checkout prev does a git checkout of the tg prev branch. For the lazy a single n or p can be used with tg checkout instead of typing out the entire next or prev. Or, for the anal, previous will also be accepted for prev.

Referring to the A...L commit graph shown above, I is the parent of J and, conversely, J is the child of I. (Git only explicitly records the child to parent links, in other words a "child" points to zero or more "parents", but parents are completely clueless about their own children.)

For historical reasons, the tg checkout command accepts child as a synonym for next and parent as a synonym for prev. However, this terminology can be confusing since Git has "parent" links but tg checkout is referring to the TopGit DAG, not Git's. Best to just avoid using child or parent to talk about navigating the TopGit DAG and reserve them strictly for discussing the Git DAG.

There may be more than one

In a simple linear history as shown above there's always only one "next" or "prev" patch. However, TopGit does not restrict one to only a linear history (although that can make patch exports just a bushel of fun).

Suffice it to say that there is always a single linearized ordering for any TopGit patch series since it's always a DAG (Directed Acyclic Graph), but it may not be immediately obvious to the casual observer what that is.

The tg checkout command will display a list to choose from if next or prev would be ambiguous.

Use the tg info/checkout --series command

To see the full, linearized, list of patches with their summary displayed in order from first to last patch in the series, just run the tg info --series command. It takes the name of any patch in the series automatically using HEAD if none is given. It even provides a nice "YOU ARE HERE" mark in the output list helpful to those who have been absent for a time engaging in otherwise distracting activities and need to be reminded where they are.

Using tg checkout --series can take you there (picking from a list) if you've forgotten the way back to wherever you're supposed to be.

Don't get pushy, there's just one more thing

For historical reasons, tg checkout with no arguments whatsoever behaves like tg checkout next. For the same historical reasons, tg checkout .. behaves like tg checkout prev (think of .. as the "parent" directory and since "parent" means "prev" in this context it will then make sense).

Now, for that one more thing. Consider that you have a pristine "upstream" tarball, repository, source dump or otherwise obtained set of unmodified source files that need to be patched. View them like so:

+-------------------------------+
| Unmodified "upstream" source  |
| files represented with "A"    |
+-------------------------------+

Now, add the first patch, 0001, to them and view the result like so:

+--------------------------+----+
| Patch 0001 represented by "F" |
+-------------------------------+
| Unmodified "upstream" source  |
| files represented with "A"    |
+-------------------------------+

Not stopping there, "push" patches 2, 3 and 4 onto the stack as well like so:

+--------------------------+----+
| Patch 0004 represented by "I" |
+--------------------------+----+
| Patch 0003 represented by "H" |
+--------------------------+----+
| Patch 0002 represented by "G" |
+--------------------------+----+
| Patch 0001 represented by "F" |
+-------------------------------+
| Unmodified "upstream" source  |
| files represented with "A"    |
+-------------------------------+

In other words, to go to the "next" patch in the series it needs to be "push"ed onto the stack. tg checkout accepts push as an alias for next.

Similarly to go to the "previous" patch in the series the current one needs to be "pop"ped off the stack. tg checkout accepts pop as an alias for prev.

Unfortunately for these aliases, in Git terminology a "push" has quite a different meaning and the tg push command does something quite different from tg checkout push. Then there's the matter of using a single letter abbreviation for the lazy -- p would mean what exactly?

tg checkout continues to accept the push and pop aliases for next and prev respectively, but it's best to avoid them since push has an alternate meaning everywhere else in TopGit and Git and that leaves pop all alone in the dark.

SEQUESTRATION

No, this is not a section about budget nonsense. ;)

TopGit keeps its metadata in .topdeps and .topmsg files. In an effort to facilitate cherry-picking and other Git activities on the patch changes themselves while ignoring the TopGit metadata, TopGit attempts to keep all changes to .topdeps and .topmsg files limited to commits that do NOT contain changes to any other files.

This is a departure from previous TopGit versions that made no such effort.

Primarily this affects tg create and tg import (which makes use of tg create) as tg create will commit the initial versions of .topdeps and .topmsg for a new TopGit-controlled branch in their own commit instead of mixing them in with changes to other files.

The pre-commit hook will also attempt to separate out any .topdeps and .topmsg changes from commits that include changes to other files.

It is possible to defeat these checks without much effort (pre-commit hooks can easily be bypassed, tg create has a --no-commit option, many Git commands simply do not run the pre-commit hook, etc.).

If you really, really, really, really want to change the default back to the old behavior of previous TopGit versions where no such sequestration took place, then set the topgit.sequester config variable explicitly to the value false. But this is not recommended.

AMENDING AND REBASING AND UPDATE-REF'ING

In a word, "don't".

It is okay to manually update a top-bases/... ref when a) it has no depedencies (i.e. it was created with the tg create --base option) and b) the old top-bases/... ref value can be fast-forwarded to the new top-bases/... value OR the new value contains ALL of the changes in the old value through some other mechanism (perhaps they were cherry-picked or otherwise applied to the new top-bases/... ref). The same rules apply to non-TopGit-controlled dependencies. Use the tg update --base <branch> <new-ref> command to safely make such an update while making it easy to set the merge commit message at the same time.

Ignoring this rule and proceeding anyway with a non-fast-forward update to a top-bases/... ref will result in changes present in the new value being merged into the branch (at tg update time) as expected (possibly with conflicts), but any changes that were contained in the old version of the top-bases/... ref which have been dropped (i.e. are NOT contained in the new version of the top-bases/... ref) will continue to be present in the branch! To get rid of the dropped commits, one or more "revert" commits will have to be manually applied to the tip of the new top-bases/... value (which will then be merged into the branch at next tg update time).

The only time it's safe to amend, rebase, filter or otherwise rewrite commits contained in a TopGit controlled branch or non-TopGit branch is when those commits are NOT reachable via any other ref!

Furthermore, while it is safe to rewrite merge commits (provided they meet the same conditions) the merge commits themselves and the branches they are merging in must be preserved during the rewrite and that can be rather tricky to get right so it's not recommended.

For example, if, while working on a TopGit-controlled branch foo, a bad typo is noticed, it's okay to ammend/rebase to fix that provided neither tg update nor tg create has already been used to cause some other ref to be able to reach the commit with the typo.

If an amend or rewrite is done anyway even though the commit with the typo is reachable from some other ref, the typo won't really be removed. What will happen instead is that the new version without the typo will ultimately be merged into the other ref(s) (at tg update time) likely causing a conflict that will have to be manually resolved and the commit with the typo will continue to be reachable from those other refs!

Instead just make a new commit to fix the typo. The end result will end up being the same but without the merge conflicts.

See also the discussion in the NO UNDO section.

BARE BRANCHES

A "TopGit bare branch" (or just "bare branch" for short), refers to a TopGit branch that has neither a .topdeps nor a .topmsg file stored in it. And it's neither a new, still-empty empty branch nor an annihilated branch.

Such branches are not recommended but are reluctantly accomodated.

There are three situtations in which TopGit may encounter a TopGit branch that has neither a .topdeps nor a .topmsg file.

  1. Branch creation with --no-commit
    Before the initial commit is made, the branch will still be pointing to the same commit as its "top-bases" ref. Branches in this condition (where the branch and top-bases ref point to the same commit) show up as having "No commits" in listings.
  2. Annihilated branches
    A branch is annihilated by making a new commit on the branch that makes its tree identical to the tree of its corresponding top-bases ref. Although the trees will be the same, the commits will be different and annihilated branches are distinguished from "No commits" branches in this way. Annihilated branches are generally invisible and do not show up in listings or other status displays. Intentionally so.
  3. Bare branches
    Any TopGit branch with neither a .topdeps file nor a .topmsg file whose branch and top-bases trees differ falls into this category. TopGit will not create such a branch itself nor does it provide any commands to do so.

Whenever possible, a TopGit "[BASE]" branch should be preferred to using a "bare branch" because a) it can never be mistaken for an annihilated branch, b) it has a nice subject attached (via its .topmsg file) that shows up in listings and c) exactly when and which updates are taken can be planned.

Nevertheless, situations may arise where it's useful to have TopGit treat a branch as a "TopGit branch" so that it fully participates in all update activities (such as updating local branches based on their remote branches), but it's not feasible to turn it into a real "TopGit branch" as it comes from an external source and rather than controlling exactly when and what updates are picked up from it by TopGit (the precise use case of a "[BASE]" branch), all updates that appear on it are to be assimilated as soon as they occur.

For this reason, TopGit will accomodate such "bare branches" but it will not create (nor provide the means to create) them itself.

In order to create a "bare branch" all that's required is to create the necessary top-bases ref. The choice of commit for the top-bases ref will affect the output of the "files", "log" and "patch" commands most directly (but all commands will be affected).

To work properly as a "bare branch", the commit the "bare branch"'s base points to should be contained within the branch, be a different commit than the branch tip itself and have a different tree than the branch tip. Simply setting the base to the parent commit of the "bare branch" will usually work, but should that commit at the tip of the "bare branch" end up getting reverted as the next commit, the trees would match and it would appear to be an annihilated branch rather than a "bare branch". That is one of the reasons these branches are not recommended in the first place.

Setting the base to the root commit of the branch is more reliable and may be accomplished like so for a local branch named "mybranch":

git update-ref $(tg --top-bases)/mybranch \
  $(git rev-list --first-parent --max-parents=0 mybranch) ""

Typically though it's more likely a remote bare branch will be needed. For a remote named "origin" and a remote branch name of "vendor" this will do it:

git update-ref $(tg --top-bases -r origin)/vendor \
  $(git rev-list --first-parent --max-parents=0 origin/vendor) ""

Such "bare branches" are not likely ever to receive any more direct support in TopGit than acknowleging they can be useful in some situations and tolerating their existence by functioning properly with them even to the point of the pre-commit hook tacitly allowing continued commits on such branches without complaints about missing .topdeps and .topmsg files.

Note, however, that creating a regular TopGit branch that has no changes of its own with the "bare branch" as its single dependency provides a means to supply some kind of documentation if all other uses of the "bare branch" depend on this "wrapper" branch instead of directly on the "bare branch".

SPEED AND CACHING

TopGit needs to check many things to determine whether a TopGit branch is up-to-date or not. This can involve a LOT of git commands for a complex dependency tree. In order to speed things up, TopGit keeps a cache of results in a tg-cache subdirectory in the .git directory.

Results are tagged with the original hash values used to get that result so that items which have not been changed return their results quickly and items which have been changed compute their new result and cache it for future use.

The .git/tg-cache directory may be removed at any time and the cache will simply be recreated in an on-demand fashion as needed, at some speed penalty, until it's fully rebuilt.

To force the cache to be fully pre-loaded, run the tg summary command without any arguments. Otherwise, normal day-to-day TopGit operations should keep it more-or-less up-to-date.

While each TopGit command is running, it uses a temporary subdirectory also located in the .git directory. These directories are named tg-tmp.XXXXXX where the XXXXXX part will be random letters and digits.

These temporary directories should always be removed automatically after each TopGit command finishes running. As long as you are not in a subshell as a result of a TopGit command stopping and waiting for a manual merge resolution, it's safe to remove any of these directories that may have somehow accidentally been left behind as a result of some failure that occurred while running a TopGit command (provided, of course, it's not actually being used by a TopGit command currently running in another terminal window or by another user on the same repository).

USAGE

tg [global options] <subcommand> [<subcommand option/argument>...]

Global options:

[-C <dir>]... [-r <remote> | -u] [-c <name>=<val>]... [--[no-]pager]

-C <dir> Change directory to <dir> before doing anything more
-r <remote> Pretend topgit.remote is set to <remote>
-u Pretend topgit.remote is not set
-c <name=val> Pass config option to git, may be repeated
-w <tgtag> Activate wayback machine using the tg tag <tgtag>
--no-pager Disable use of any pager (by both TopGit and Git)
--pager Enable use of a pager (aka -p)
--top-bases Show full top-bases ref prefix and exit
--exec-path Show path to subcommand scripts location and exit
--help Show brief usage help and exit (aka -h)

The tg tool has several subcommands:

tg annihilate:Mark a TopGit-controlled branch as defunct
tg base:Show base commit for one or more TopGit branches
tg checkout:Shortcut for git checkout with name matching
tg contains:Which TopGit-controlled branch contains the commit
tg create:Create a new TopGit-controlled branch
tg delete:Delete a TopGit-controlled branch cleanly
tg depend:Add a new dependency to a TopGit-controlled branch
tg export:Export TopGit branch patches to files or a branch
tg files:Show files changed by a TopGit branch
tg help:Show TopGit help optionally using a browser
tg import:Import commit(s) to separate TopGit branches
tg info:Show status information about a TopGit branch
tg log:Run git log limiting revisions to a TopGit branch
tg mail:Shortcut for git send-email with tg patch output
tg migrate-bases:Transition top-bases to new location
tg next:Show branches directly depending on a TopGit branch
tg patch:Generate a patch file for a TopGit branch
tg prev:Show non-annihilated TopGit dependencies for a branch
tg push:Run git push on TopGit branch(es) and depedencies
tg rebase:Auto continue git rebase if rerere resolves conflicts
tg remote:Set up remote for fetching/pushing TopGit branches
tg revert:Revert ref(s) to a state stored in a tg tag
tg shell:Extended wayback machine mode
tg status:Show current TopGit status (e.g. in-progress update)
tg summary:Show various information about TopGit branches
tg tag:Create tag that records current TopGit branch state
tg update:Update TopGit branch(es) with respect to dependencies

tg help

Our sophisticated integrated help facility. Mostly duplicates what is below:

# to list commands:
$ tg help
# to get help for a particular command:
$ tg help <command>
# to get help for a particular command in a browser window:
$ tg help -w <command>
# to get help on TopGit itself
$ tg help tg
# to get help on TopGit itself in a browser
$ tg help -w tg

tg status

Our sophisticated status facility. Similar to Git's status command but shows any in-progress update that's awaiting a merge resolution or any other on-going TopGit activity (such as a branch creation).

With a single --verbose (or -v) option include a short status display for any dirty (but not untracked) files. This also causes all non file status lines to be prefixed with "## ".

With two (or more) --verbose (or -v) options, additionally show full symbolic ref names and unabbreviated hash values.

With the --exit-code option the exit code will be non-zero if any TopGit or Git operation is currently in progress or the working tree is unclean.

tg create

Create a new TopGit-controlled topic branch of the given name (required argument) and switch to it. If no dependencies are specified (by extra arguments passed after the first one), the current branch is assumed to be the only dependency.

By default tg create opens an editor on the new .topmsg file and then commits the new .topmsg and .topdeps files automatically with a suitable default commit message.

The commit message can be changed with the -m (or --message) or -F (or --file) option. The automatic commit can be suppressed by using the --no-ccmmit (or -n) option. Running the editor on the new .topmsg file can be suppressed by using --no-edit (which does NOT suppress the automatic commit unless --no-commit is also given) or by providing an explicit value for the new .topmsg file using the --topmsg or --topmsg-file option. In any case the .topmsg content will be automatically reformated to have a Subject: header line if needed.

If the format.signoff config variable (see git help config) has been set to true then the Signed-off-by: header line added to the end of the initial version of the .topmsg file will be uncommented by default. Otherwise it will still be there but will be commented out and will be automatically stripped if no action is taken to remove the comment character.

If more than one dependency is listed an automatic tg update runs after the branch has been created to merge in the additional dependencies and bring the branch up-to-date. This can be suppressed with the --no-commit option (which also suppresses the initial commit) or the --no-update option (which allows the initial commit while suppressing only the update operation portion).

Previous versions of TopGit behaved as though both the --no-edit and --no-commit options were always given on the command line.

The default behavior has been changed to promote a separation between commits that modify .topmsg and/or .topdeps and commits that modify other files. This facilitates cleaner cherry picking and other patch maintenance activities.

You should edit the patch description (contained in the .topmsg file) as appropriate. It will already contain some prefilled bits. You can set the topgit.to, topgit.cc and topgit.bcc git configuration variables (see man git-config) in order to have tg create add these headers with the given default values to .topmsg before invoking the editor. If the configuration variable topgit.subjectPrefix is set its value will be inserted between the initial [ and the word PATCH in the subject line (with a space added before the word PATCH of course).

The main task of tg create is to set up the topic branch base from the dependencies. This may fail due to merge conflicts if more than one dependency is given. In that case, after you commit the conflict resolution, you should call tg update --continue to finish merging the dependencies into the new topic branch base.

With the --base (aka --no-deps) option at most one dependency may be listed which may be any valid committish (instead of just refs/heads/...) and the newly created TopGit-controlled branch will have an empty .topdeps file. This may be desirable in order to create a TopGit-controlled branch that has no changes of its own and serves merely to mark the common dependency that all other TopGit-controlled branches in some set of TopGit-controlled branches depend on. A plain, non-TopGit-controlled branch can be used for the same purpose, but the advantage of a TopGit-controlled branch with no dependencies is that it will be pushed with tg push, it will show up in the tg summary and tg info output with the subject from its .topmsg file thereby documenting what it's for and finally it can be set up with tg create -r and/or tg remote --populate to facilitate sharing.

For example, tg create --base release v2.1 will create a TopGit- controlled release branch based off the v2.1 tag that can then be used as a base for creation of other TopGit-controlled branches. Then when the time comes to move the base for an entire set of changes up to v2.2 the command tg update --base release v2.2 can be used followed by tg update --all.

Using --base it's also possible to use tg create on an unborn branch (omit the dependency name or specify HEAD). The unborn branch itself can be made into the new TopGit branch (rather than being born empty and then having the new TopGit branch based off that) by specifying HEAD as the new branch's name (which is probably what you normally want to do in this case anyway so you can just run tg create --base HEAD to accomplish that).

In an alternative use case, if -r <branch> is given instead of a dependency list, the topic branch is created based on the given remote branch. With just -r the remote branch name is assumed to be the same as the local topic branch being created. Since no new commits are created in this mode (only two refs will be updated) the editor will never be run for this use case. Note that no other options may be combined with -r.

The --quiet (or -q) option suppresses most informational messages.

tg delete

Remove a TopGit-controlled topic branch of the given name (required argument). Normally, this command will remove only an empty branch (base == head) without dependents; use -f to remove a non-empty branch or a branch that is depended upon by another branch.

The -f option is also useful to force removal of a branch's base, if you used git branch -D B to remove branch B, and then certain TopGit commands complain, because the base of branch B is still there.

Normally tg delete will refuse to delete the current branch. However, giving -f twice (or more) will force it to do so but it will first detach your HEAD.

IMPORTANT: Currently, this command will NOT remove the branch from the dependency list in other branches. You need to take care of this manually. This is even more complicated in combination with -f -- in that case, you need to manually unmerge the removed branch's changes from the branches depending on it.

The same --stash and --no-stash options are accepted with the same exact semantics as for tg update.

See also tg annihilate.

TODO: -a to delete all empty branches, depfix, revert

tg annihilate

Make a commit on the current or given TopGit-controlled topic branch that makes it equal to its base, including the presence or absence of .topmsg and .topdeps. Annihilated branches are not displayed by tg summary, so they effectively get out of your way. However, the branch still exists, and tg push will push it (except if given the -a option). This way, you can communicate that the branch is no longer wanted.

When annihilating a branch that has dependents (i.e. branches that depend on it), those dependents have the dependencies of the branch being annihilated added to them if they do not already have them as dependencies. Essentially the DAG is repaired to skip over the annihilated branch.

Normally, this command will remove only an empty branch (base == head, except for changes to the .top* files); use -f to annihilate a non-empty branch.

After completing the annihilation itself, normally tg update is run on any modified dependents. Use the --no-update option to suppress running tg update.

The same --stash and --no-stash options are accepted with the same exact semantics as for tg update.

tg depend

Change the dependencies of a TopGit-controlled topic branch. This should have several subcommands, but only add is supported right now.

The add subcommand takes an argument naming a topic branch to be added, adds it to .topdeps, performs a commit and then updates your topic branch accordingly. If you want to do other things related to the dependency addition, like adjusting .topmsg, use the option --no-commit. Adding the --no-update (or --no-commit) option will suppress the tg update normally performed after committing the change.

It is safe to run tg depend add in a dirty worktree, but the normally performed tg update will be suppressed in that case (even if neither --no-update nor --no-commit is given).

You have enabled git rerere haven't you?

TODO: Subcommand for removing dependencies, obviously

tg files

List files changed by the current or specified topic branch.

Options:
-i list files based on index instead of branch
-w list files based on working tree instead of branch

tg info

Show summary information about the current or specified topic branch.

Numbers in parenthesis after a branch name such as "(11/3 commits)" indicate how many commits on the branch (11) and how many of those are non-merge commits (3).

With --verbose (or -v) include a list of dependents (i.e. other branches that depend on this one). Another --verbose annotates them with "[needs merge]" if the current tip of branch for which info is being shown has not yet been merged into the base of the dependent. Two --verbose options also cause annihilated dependencies to be shown in the "Depends:" list.

Alternatively, if --heads is used then which of the independent TopGit branch heads (as output by tg summary --topgit-heads) logically contains the specified commit (which may be any committish -- defaults to HEAD if not given). Zero or more results will be output. Note that "logically" means with regard to the TopGit dependency relationships as established by the .topdeps file(s). It's the answer that would be given when all the TopGit branches are up-to-date (even though they need not be to use this option) and the git branch --contains command is run and the output then filtered to only those branches that appear in tg summary --topgit-heads. This computation may require several seconds on complex repositories.

If --leaves is used then the unique list of leaves of the current or specified topic branch is shown as one fully-qualified ref per line. Duplicates are suppressed and a tag name will be used when appropriate. A "leaf" is any dependency that is either not a TopGit branch or is the base of a non-annihilated TopGit branch with no non-annihilated dependencies.

The --deps option shows non-annihilated TopGit dependencies of the specified branch (default is HEAD). (It can also be spelled out as --dependencies for the pedantically inclined.)

The --dependents option shows non-annihilated TopGit dependents (i.e. branches that depend on the specified branch). The default branch to operate on is again HEAD.

A linearized patch series can only be automatically created for a TopGit topic branch (including its recursive dependencies) when exactly one line is output by tg info --leaves <topic-branch>.

With --series the list of TopGit branches in the order they would be linearized into a patch series is shown along with the description of each branch. If the branch name passed to tg info is not the last branch in the series a marker column will be provided to quickly locate it in the list. This same option can be used with tg checkout.

Some patches shown in the list may not actually end up introducing any changes if exported and will therefore end up being omitted. The 0 indicator in tg summary output can help to identify some of these.

The patches shown in the series in the order they are shown form the basis for the tg next and tg prev operations with the first patch shown being considered the first and so on up to the last.

Options:
-i Use TopGit metadata from the index instead of the branch
-w Use TopGit metadata from the working tree instead of the branch

tg patch

Generate a patch from the current or specified topic branch. This means that the diff between the topic branch base and head (latest commit) is shown, appended to the description found in the .topmsg file.

The patch is simply dumped to stdout. In the future, tg patch will be able to automatically send the patches by mail or save them to files. (TODO)

Options:
-i base patch generation on index instead of branch
-w base patch generation on working tree instead of branch
--binary pass --binary to git diff-tree to enable generation of binary patches
--quiet be quiet (aka -q) about missing and unfixed From:
--from make sure patch has a From: line, if not add one
--from=<a> <a> or Signed-off-by value or ident value; git am really gets unhappy with patches missing From: lines; will NOT replace an existing non-empty From: header
--no-from leave all From: lines alone, missing or not (default)
--diff-opt options after the branch name (and an optional --) are passed directly to git diff-tree

In order to pass a sole explicit -w through to git diff-tree it must be separated from the tg options by an explicit --. Or it can be spelled as --ignore-all-space to distinguuish it from tg's -w option.

If the config variable topgit.from is set to a boolean it can be used to enable or disable the --from option by default. If it's set to the special value quiet the --quiet option is enabled and From: lines are left alone by default. Any other non-empty value is taken as a default --from=<value> option. The --no-from option will temporarily disable use of the config value.

If additional non-tg options are passed through to git diff-tree (other than --binary which is fully supported) the resulting tg patch output may not be appliable.

tg mail

Send a patch from the current or specified topic branch as email(s).

Takes the patch given on the command line and emails it out. Destination addresses such as To, Cc and Bcc are taken from the patch header.

Since it actually boils down to git send-email, please refer to the documentation for that for details on how to setup email for git. You can pass arbitrary options to this command through the -s parameter, but you must double-quote everything. The -r parameter with a msgid can be used to generate in-reply-to and reference headers to an earlier mail.

WARNING: be careful when using this command. It easily sends out several mails. You might want to run:

git config sendemail.confirm always

to let git send-email ask for confirmation before sending any mail.

Options:
-i base patch generation on index instead of branch
-w base patch generation on working tree instead of branch
TODO: tg mail patchfile to mail an already exported patch
TODO: mailing patch series
TODO: specifying additional options and addresses on command line

tg remote

Register the given remote as TopGit-controlled. This will create the namespace for the remote branch bases and teach git fetch to operate on them. However, from TopGit 0.8 onwards you need to use tg push, or git push --mirror, for pushing TopGit-controlled branches.

tg remote takes an optional remote name argument, and an optional --populate switch. Use --populate for your origin-style remotes: it will seed the local topic branch system based on the remote topic branches. --populate will also make tg remote automatically fetch the remote, and tg update look at branches of this remote for updates by default.

Using --populate with a remote name causes the topgit.remote git configuration variable to be set to the given remote name.

tg summary

Show overview of all TopGit-tracked topic branches and their up-to-date status. With a branch name limit output to that branch. Using --deps-only or --rdeps changes the default from all branches to just the current HEAD branch but using --all as the branch name will show results for all branches instead of HEAD.

>
marks the current topic branch
0
indicates that it introduces no changes of its own
l/r
indicates respectively whether it is local-only or has a remote mate
L/R
indicates respectively if it is ahead or out-of-date with respect to its remote mate
D
indicates that it is out-of-date with respect to its dependencies
!
indicates that it has missing dependencies [even if they are recursive ones]
B
indicates that it is out-of-date with respect to its base
*
indicates it is ahead of (and needs to be merged into) at least one of its dependents -- only computed when showing all branches or using the (possibly implied) --with-deps option.

This can take a longish time to accurately determine all the relevant information about each branch; you can pass -t (or -l or --list) to get just a terse list of topic branch names quickly. Also adding --verbose (or -v) includes the subjects too. Adding a second --verbose includes annihilated branches as well.

Passing --heads shows independent topic branch names and when combined with --rdeps behaves as though --rdeps were run with the output of --heads.

The --heads-independent option works just like --heads except that it computes the heads using git merge-base --independent rather than examining the TopGit .topdeps relationships. If the TopGit branches are all up-to-date (as shown in tg summary) then both --heads and --heads-independent should compute the same list of heads (unless some overlapping TopGit branches have been manually created). If not all the TopGit branches are up-to-date then the --heads-independent results may have extra items in it, but occasionally that's what's needed; usually it's the wrong answer. (Note that --topgit-heads is accepted as an alias for --heads as well.)

Using --heads-only behaves as though the output of --heads was passed as the list of branches along with --without-deps.

Alternatively, you can pass --graphviz to get a dot-suitable output for drawing a dependency graph between the topic branches.

You can also use the --sort option to sort the branches using a topological sort. This is especially useful if each TopGit-tracked topic branch depends on a single parent branch, since it will then print the branches in the dependency order. In more complex scenarios, a text graph view would be much more useful, but that has not yet been implemented.

The --deps option outputs dependency information between branches in a machine-readable format. Feed this to tsort to get the output from --sort.

The --deps-only option outputs a sorted list of the unique branch names given on the command line plus all of their recursive dependencies (subject to --exclude of course). When --deps-only is given the default is to just display information for HEAD, but that can be changed by using --all as the branch name. Each branch name will appear only once in the output no matter how many times it's visited while tracing the dependency graph or how many branch names are given on the command line to process.

The --rdeps option outputs dependency information in an indented text format that clearly shows all the dependencies and their relationships to one another. When --rdeps is given the default is to just display information for HEAD, but that can be changed by using --all as the branch name or by adding the --heads option. Note that tg summary --rdeps --heads can be particularly helpful in seeing all the TopGit-controlled branches in the repository and their relationships to one another.

Note that --rdeps has two flavors. The first (and default) is --rdeps-once which only shows the dependencies of a branch when it's first visited. For example, if D depends on several other branches perhaps recursively and both branch A and B depend on D, then whichever of A or B is shown first will show the entire dependency chain for D underneath it and the other one will just show a line for D itself with a "^" appended to indicate that the rest of the deps for D can be found above. This can make the output a bit more compact without actually losing any information which is why it's the default. However, using the --rdeps-full variant will repeat the full dependency chain every time it's encountered.

Adding --with-deps replaces the given list of branches (which will default to HEAD if none are given) with the result of running tg summary --deps-only --tgish on the list of branches. This can be helpful in limiting tg summary output to only the list of given branches and their dependencies when many TopGit-controlled branches are present in the repository. Use --without-deps to switch back to the old behavior.

The --with-related option extends (and therefore implies) --with-deps. First the list of branches (which will default to HEAD if none are given) is replaced with the result of running tg summary --heads (aka --topgit-heads) and the result is then processed as though it had been specified using --with-deps.

When it would be allowed, --with-deps is now the default. But, if in addition, exactly one branch is specified (either explicitly or implicitly) and it's spelled exactly as HEAD or @ then the default --with-deps will be promoted to a default --with-related instead. Since duplicate branches are removed before processing, explicitly listing @ twice provides an easy way to defeat this automatic promotion and ask for --with-deps on the HEAD symbolic ref with minimal typing when --with-related isn't really wanted and typing the full --with-deps option is too hard.

With --exclude branch, branch can be excluded from the output meaning it will be skipped and its name will be omitted from any dependency output. The --exclude option may be repeated to omit more than one branch from the output. Limiting the output to a single branch that has been excluded will result in no output at all.

The --tgish-only option behaves as though any non-TopGit-controlled dependencies encountered during processing had been listed after an --exclude option.

Note that the branch name can be specified as HEAD or @ as a shortcut for the TopGit-controlled branch that HEAD is a symbolic ref to. The tg summary @ and tg summary @ @ commands can be quite useful.

Options:
-i Use TopGit metadata from the index instead of the branch
-w Use TopGit metadata from the working tree instead of the branch

tg contains

Search all TopGit-controlled branches (and optionally their remotes) to find which TopGit-controlled branch contains the specified commit.

This is more than just basic branch containment as provided for by the git branch --contains command. While the shown branch name(s) will, indeed, be one (or more) of those output by the git branch --contains command, the result(s) will exclude any TopGit-controlled branches from the result(s) that have one (or more) of their TopGit dependencies (either direct or indirect) appearing in the git branch --contains output.

Normally the result will be only the one, single TopGit-controlled branch for which the specified committish appears in the tg log output for that branch (unless the committish lies outside the TopGit-controlled portion of the DAG and --no-strict was used).

Unless --annihilated-okay (or --ann or --annihilated) is used then annihilated branches will be immediately removed from the git branch --contains output before doing anything else. This means a committish that was originally located in a now-annihilated branch will show up in whatever branch picked up the annihilated branch's changes (if there is one). This is usually the correct answer, but occasionally it's not; hence this option. If this option is used together with --verbose then annihilated branches will be shown as "[:annihilated:]".

In other words, if a tg patch is generated for the found branch (assuming one was found and a subsequent commit in the same branch didn't then revert or otherwise back out the change), then that patch will include the changes introduced by the specified committish (unless, of course, that committish is outside the TopGit-controlled portion of the DAG and --no-strict was given).

This can be very helpful when, for example, a bug is discovered and then after using git bisect (or some other tool) to find the offending commit it's time to commit the fix. But because the TopGit merging history can be quite complicated and maybe the one doing the fix wasn't the bug's author (or the author's memory is just going), it can sometimes be rather tedious to figure out which TopGit branch the fix belongs in. The tg contains command can quickly tell you the answer to that question.

With the --remotes (or -r) option a TopGit-controlled remote branch name may be reported as the result but only if there is no non-remote branch containing the committish (this can only happen if at least one of the TopGit-controlled local branches are not yet up-to-date with their remotes).

With the --verbose option show which TopGit DAG head(s) (one or more of the TopGit-controlled branch names output by tg summary --heads) have the result as a dependency (either direct or indirect). Using this option will noticeably increase running time.

With the default --strict option, results for which the base of the TopGit-controlled branch contains the committish will be suppressed. For example, if the committish was deep-down in the master branch history somewhere far outside of the TopGit-controlled portion of the DAG, with --no-strict, whatever TopGit-controlled branch(es) first picked up history containing that committish will be shown. While this is a useful result it's usually not the desired result which is why it's not the default.

To summarize, even with --remotes, remote results are only shown if there are no non-remote results. Without --no-strict (because --strict is the default) results outside the TopGit-controlled portion of the DAG are never shown and even with --no-strict they will only be shown if there are no --strict results. Finally, the TopGit head info shown with --verbose only ever appears for local (i.e. not a remote branch) results. Annihilated branches are never considered possible matches without --annihilated-okay.

tg checkout

Switch to a topic branch. You can use git checkout <branch> to get the same effect, but this command helps you navigate the dependency graph, or allows you to match the topic branch name using a regular expression, so it can be more convenient.

The --branch (or -b or --branch=<name>) option changes the default starting point from HEAD to the specified branch.

For the "next" and "previous" commands, the <steps> value may be --all (or -a) to take "As many steps As possible" or "step ALL the way" or "ALL steps at once" (or make something better up yourself).

The following subcommands are available:

tg checkout next [<steps>]
Check out a branch that directly depends on your current branch. Move <steps> (default 1) step(s) in the "next" direction (AKA n).
tg checkout prev [<steps>]
Check out a branch that this branch directly depends on. Move <steps> (default 1) step(s) in the "previous" direction (AKA p or previous).
tg checkout [goto] [--] <pattern>
Check out a topic branch that matches <pattern>. <pattern> is used as a grep ERE pattern to filter all the topic branches. Both goto and -- may be omitted provided <pattern> is not -a, --all, -h, --help, goto, --, n, next, push, child, p, prev, previous, pop, parent, +, - or ...
tg checkout [goto] [--] --series[=<head>]
Check out a topic branch that belongs to the current (or <head>) patch series. A list with descriptions (tg info --series) will be shown to choose from if more than one.
tg checkout + [<steps>]
An alias for next.
tg checkout push [<steps>]
An alias for next.
tg checkout child [<steps>]
Deprecated alias for next.
tg checkout
Semi-deprecated alias for next.
tg checkout - [<steps>]
An alias for prev.
tg checkout pop [<steps>]
An alias for prev.
tg checkout parent [<steps>]
Deprecated alias for prev.
tg checkout .. [<steps>]
Semi-deprecated alias for prev.

If any of the above commands can find more than one possible branch to switch to, you will be presented with the matches and asked to select one of them.

If the --ignore-other-worktrees (or --iow) option is given and the current Git version is at least 2.5.0 then the full --ignore-other-worktrees option will be passed along to the git checkout command when it's run (otherwise the option will be silently ignored and not passed to Git as it would cause an error).

The --force (or -f) option, when given, gets passed through to the git checkout command.

The --merge (or -m) option, when given, gets passed through to the git checkout command.

The --quiet (or -q) option, when given, gets passed through to the git checkout command.

The <pattern> of tg checkout goto is optional. If you don't supply it, all the available topic branches are listed and you can select one of them.

Normally, the next and prev commands move one step in the dependency graph of the topic branches. The -a option causes them (and their aliases) to move as far as possible. That is, tg checkout next -a moves to a topic branch that depends (directly or indirectly) on the current branch and that no other branch depends on. tg checkout prev -a moves to a topic branch that the current topic branch depends on (directly or indirectly). If there is more than one possibility, you will be prompted for your selection.

See also NAVIGATION.

tg export

Export a tidied-up history of the current topic branch and its dependencies, suitable for feeding upstream. Each topic branch corresponds to a single commit or patch in the cleaned up history (corresponding basically exactly to tg patch output for the topic branch).

The command has three possible outputs now -- either a Git branch with the collapsed history, a Git branch with a linearized history, or a quilt series in new directory.

In the case where you are producing collapsed history in a new branch, you can use this collapsed structure either for providing a pull source for upstream, or for further linearization e.g. for creation of a quilt series using git log:

git log --pretty=email -p --topo-order origin..exported

To better understand the function of tg export, consider this dependency structure:

origin/master - t/foo/blue - t/foo/red - master
             `- t/bar/good <,----------'
             `- t/baz      ------------'

(where each of the branches may have a hefty history). Then:

master$ tg export for-linus

will create this commit structure on the branch for-linus:

origin/master - t/foo/blue -. merge - t/foo/red -.. merge - master
             `- t/bar/good <,-------------------'/
             `- t/baz      ---------------------'

In this mode, tg export works on the current topic branch, and can be called either without an option (in that case, --collapse is assumed), or with the --collapse option, and with one mandatory argument: the name of the branch where the exported result will be stored.

Both the --collapse and --linearize modes also accept a -s <mode> option to specify subject handling behavior for the freshly created commits. There are five possible modes:

keep:Like git mailinfo -k
mailinfo:Like git mailinfo
patch:Remove first [PATCH*] if any
topgit:Remove first [PATCH*], [BASE], [ROOT] or [STAGE]
trim:Trim runs of spaces/tabs to a single space

The topgit (aka tg) mode is the default (quelle surprise) and like the patch mode will only strip the first square brackets tag (if there is one) provided it's a TopGit-known tag (the patch variation will only strip a PATCH tag but still just the first one). Note that TopGit does understand [RELEASE] in topgit mode. With trim (aka ws) internal runs of spaces/tabs are converted to a single space, but no square brackets tags are removed. The ws mode should generally be preferred instead of using keep mode. All modes always remove leading/trailing spaces and tabs and if the topgit.subjectPrefix value (see tg create) has been set both the topgit and patch modes will match tags with that prefix too.

Setting the config variable topgit.subjectMode to one of the mode values shown above will change the default to that mode.

When using the linearize mode:

master$ tg export --linearize for-linus

you get a linear history respecting the dependencies of your patches in a new branch for-linus. The result should be more or less the same as using quilt mode and then reimporting it into a Git branch. (More or less because the topological order can usually be extended in more than one way into a total order, and the two methods may choose different ones.) The result might be more appropriate for merging upstream, as it contains fewer merges.

Note that you might get conflicts during linearization because the patches are reordered to get a linear history. If linearization would produce conflicts then using --quilt will also likely result in conflicts when the exported quilt series is applied. Since the --quilt mode simply runs a series of tg patch commands to generate the patches in the exported quilt series and those patches will end up being applied linearly, the same conflicts that would be produced by the --linearize option will then occur at that time.

To avoid conflicts produced by --linearize (or by applying the --quilt output), use the default --collapse mode and then use tg rebase (or git rebase -m directly) on the collapsed branch (with a suitable <upstream>) followed by git format-patch on the rebased result to produce a conflict-free patch set. A suitable upstream may be determined with the tg info --leaves command (if it outputs more than one line, linearization will be problematic).

You have enabled git rerere haven't you?

When using the quilt mode:

master$ tg export --quilt for-linus

would create the following directory for-linus:

for-linus/t/foo/blue.diff
for-linus/t/foo/red.diff
for-linus/t/bar/good.diff
for-linus/t/baz.diff
for-linus/series:
       t/foo/blue.diff -p1
       t/bar/good.diff -p1
       t/foo/red.diff -p1
       t/baz.diff -p1

With --quilt, you can also pass the -b parameter followed by a comma-separated explicit list of branches to export, or the --all parameter (which can be shortened to -a) to export them all. The --binary option enables producing Git binary patches. These options are currently only supported with --quilt.

In --quilt mode the patches are named like the originating topgit branch. So usually they end up in subdirectories of the output directory. With the --flatten option the names are mangled so that they end up directly in the output dir (slashes are replaced with underscores). With the --strip[=N] option the first N subdirectories (all if no N is given) get stripped off. Names are always --strip'd before being --flatten'd. With the option --numbered (which implies --flatten) the patch names get a number as prefix to allow getting the order without consulting the series file, which eases sending out the patches.

Note that tg export is fully compatible with the wayback machine and when used with the --collapse or --linearize options will "push" the resulting branch back into the main repository when used in wayback mode.

TODO: Make stripping of non-essential headers configurable
TODO: --mbox option to export instead as an mbox file
TODO: support --all option in other modes of operation
TODO: For quilt exporting, export the linearized history created in a temporary branch--this would allow producing conflict-less series

tg import

Import commits within the given revision range(s) into TopGit, creating one topic branch per commit. The dependencies are set up to form a linear sequence starting on your current branch -- or a branch specified by the -d parameter, if present.

The branch names are auto-guessed from the commit messages and prefixed by t/ by default; use -p <prefix> to specify an alternative prefix (even an empty one).

Each "<range>" must be of the form <rev1>..<rev2> where either <rev1> or <rev2> can be omitted to mean HEAD. Additionally the shortcut <rev>^! (see git help revisions) is permitted as a "<range>" to select the single commit <rev> but only if the commit <rev> has exactly one parent. This is really just a shortcut for <rev>^..<rev> but somewhat safer since it will fail if <rev> has other than one parent.

Alternatively, you can use the -s NAME parameter to specify the name of the target branch; the command will then take one more argument describing a single commit to import (which may have any number of parents).

tg update

Update the current, specified or all topic branches with respect to changes in the branches they depend on and remote branches. This is performed in two phases -- first, changes within the dependencies are merged to the base, then the base is merged into the topic branch. The output will guide you on what to do next in case of conflicts.

You have enabled git rerere haven't you?

The --[no-]auto[-update] options together with the topgit.setAutoUpdate config item control whether or not TopGit will automatically temporarily set rerere.autoUpdate to true while running tg update. The default is true. Note that this does not enable Git's rerere feature, it merely makes it automatically stage any previously resolved conflicts. The rerere.enabled setting must still be separately enabled (i.e. set to true) for the rerere feature to do anything at all.

Using --auto[-update] makes tg update always temporarily set rerere.autoUpdate to true while running tg update. The --no-auto[-update] option prevents tg update from changing the rerere.autoUpdate setting, but if rerere.autoUpdate has already been enabled in a config file, tg update never disables it even with --no-auto. If topgit.setAutoUpdate is unset or set to true then tg update implicitly does --auto, otherwise it does --no-auto. An explicit command line --[no-]auto[-update] option causes the topgit.setAutoUpdate setting to be ignored.

When both rerere.enabled and rerere.autoUpdate are set to true then tg update will be able to automatically continue an update whenever git rerere resolves all the conflicts during a merge. This can be such a huge time saver. That's why the default is to have TopGit automatically set rerere.autoUpdate to true while tg update is running (but remember, unless rerere.enabled has been set to true it won't make any difference).

When -a (or --all) is specified, updates all topic branches matched by <pattern>'s (see git-for-each-ref(1) for details), or all if no <pattern> is given. Any topic branches with missing dependencies will be skipped entirely unless --skip-missing is specified.

When --skip-missing is specified, an attempt is made to update topic branches with missing dependencies by skipping only the dependencies that are missing. Caveat utilitor.

When --stash is specified (or the topgit.autostash config value is set to true), a ref stash will be automatically created just before beginning updates if any are needed. The --no-stash option may be used to disable a topgit.autostash=true setting. See the tg tag --stash option for details.

After the update, if a single topic branch was specified, it is left as the current one; if -a was specified, it returns to the branch which was current at the beginning.

If your dependencies are not up-to-date, tg update will first recurse into them and update them.

If a remote branch update brings in dependencies on branches that are not yet instantiated locally, you can either bring in all the new branches from the remote using tg remote --populate, or only pick out the missing ones using tg create -r (tg summary will point out branches with incomplete dependencies by showing an ! next to them). TopGit will attempt to instantiate just the missing ones automatically for you, if possible, when tg update merges in the new dependencies from the remote.

Using the alternative --base mode, tg update will update the base of a specified [BASE] branch (which is a branch created by tg create using the --base option) to the specified committish (the second argument) and then immediately merge that into the branch itself using the specified message for the merge commit. If no message is specified on the command line, an editor will open. Unless --force is used the new value for the base must contain the old value (i.e. be a fast-forward update). This is for safety.

This mode makes updates to [BASE] branches quick and easy.

TODO: tg update -a -c to autoremove (clean) up-to-date branches

tg push

If -a or --all was specified, pushes all non-annihilated TopGit-controlled topic branches, to a remote repository. Otherwise, pushes the specified topic branches -- or the current branch, if you don't specify which. By default, the remote gets all the dependencies (both TopGit-controlled and non-TopGit-controlled) and bases pushed to it too. If --tgish-only was specified, only TopGit-controlled dependencies will be pushed, and if --no-deps was specified, no dependencies at all will be pushed.

All TopGit branches to be pushed must be up-to-date unless the --allow-outdated option is given. Branches are checked against the configured TopGit remote (topgit.remote) if it's set (as modified by the global -u and -r <remote> options).

The --dry-run, --force, --atomic, --signed[=...], -4 and -6 options are passed through directly to git push if given. Note that in the highly unlikely event that the branch names of all the branches being pushed do not fit on a single command line, multiple git push commands will be issued which would have the side effect of rendering --atomic not so atomic and cause more than one signature to be needed if --signed[=...] is used.

The push remote may be specified with the -r option. If no remote was specified, the configured default TopGit push remote will be used (topgit.pushRemote) or if that's unset the regular remote (topgit.remote).

Use something like this to push to an origin remote when it's set as topgit.remote while only checking for local out-of-dateness:

tg -u push -r origin <optional-branch-names-here>

tg base

Prints the base commit of each of the named topic branches, or the current branch if no branches are named. Prints an error message and exits with exit code 1 if the named branch is not a TopGit branch.

tg log

Prints the git log of the named topgit branch -- or the current branch, if you don't specify a name.

This is really just a convenient shortcut for:

git log --first-parent --no-merges $(tg base <name>)..<name>

where <name> is the name of the TopGit topic branch (or omitted for the current branch).

However, if <name> is a [BASE] branch the --no-merges option is omitted.

If --compact is used then git log-compact will be used instead of git log. The --command=<git-alias> option can be used to replace "log" with any non-whitespace-containing command alias name, --compact is just a shortcut for --command=log-compact. The git-log-compact tool may be found on its project page located at:

https://mackyle.github.io/git-log-compact

Note that the --compact or --command= option must be used before any -- or git log options to be recognized.

NOTE: if you have merged changes from a different repository, this command might not list all interesting commits.

tg tag

Creates a TopGit annotated/signed tag or lists the reflog of one.

A TopGit annotated tag records the current state of one or more TopGit branches and their dependencies and may be used to revert to the tagged state at any point in the future.

When reflogs are enabled (the default in a non-bare repository) and combined with the --force option a single tag name may be used as a sort of TopGit branch state stash. The special branch name --all may be used to tag the state of all current TopGit branches to facilitate this function and has the side-effect of suppressing the out-of-date check allowing out-of-date branches to be included.

As a special feature, --stash may be used as the tag name in which case --all is implied if no branch name is listed (instead of the normal default of HEAD), --force and --no-edit (use --edit to change that) are automatically activated and the tag will be saved to refs/tgstash instead of refs/tags/<tagname>. The --stash tag name may also be used with the -g/--reflog option.

The mostly undocumented option --allow-outdated will bypass the out-of-date check and is implied when --stash or --all is used.

A TopGit annotated/signed tag is simply a Git annotated/signed tag with a "TOPGIT REFS" section appended to the end of the tag message (and preceding the signature for signed tags). PEM-style begin and end lines surround one line per ref where the format of each line is full-hash SP ref-name. A line will be included for each branch given on the command line and each ref they depend on either directly or indirectly.

Note that when specifying branch names, if a given name is ambiguous but prefixing the branch name with refs/heads/ successfully disambiguates it, then that will be the interpretation used.

If more than one TopGit branch is given on the command line, a new commit will be created that has an empty tree and all of the given TopGit branches as parents and that commit will be tagged. If a single TopGit branch is given, then it will be tagged. If the --tree option is used then it will be used instead of an empty tree (a new commit will be created if necessary to guarantee the specified tree is what's in the commit the newly created tag refers to). The argument to the --tree option may be any valid treeish.

If exactly one of the branches to be tagged is prefixed with a tilde (~) it will be made the first parent of a consolidation commit if it is not already the sole commit needing to be tagged. If --tree is NOT used, its tree will also be used instead of the empty tree for any new consolidation commit if one is created. Note that if --tree is given explicitly its tree is always used but that does not in any way affect the choice of first parent. Beware that the ~ may need to be quoted to prevent the shell from misinterpreting it into something else.

All the options for creating a tag serve the same purpose as their Git equivalents except for two. The --refs option suppresses tag creation entirely and emits the "TOPGIT REFS" section that would have been included with the tag. If the --no-edit option is given and no message is supplied (via the -m or -F option) then the default message created by TopGit will be used without running the editor.

With -g or --reflog show the reflog for a tag. With the --reflog-message option the message from the reflog is shown. With the --commit-message option the first line of the tag's message (if the object is a tag) or the commit message (if the object is a commit) falling back to the reflog message for tree and blob objects is shown. The default is --reflog-message unless the --stash (refs/tgstash) is being shown in which case the default is then --commit-message. Just add either option explicitly to override the default.

When showing reflogs, non-tag entries are annotated with their type unless --no-type is given.

TopGit tags are created with a reflog if core.logallrefupdates is enabled (the default for non-bare repositories). Unfortunately Git is incapable of showing an annotated/signed tag's reflog (using git log -g) as it will first resolve the tag before checking to see if it has a reflog. Git can, however, show reflogs for lightweight tags (using git log -g) just fine but that's not helpful here. Use tg tag with the -g or --reflog option to see the reflog for an actual tag object. This also works on non-TopGit annotated/signed tags as well provided they have a reflog.

The number of entries shown may be limited with the -n option. If the tagname is omitted then --stash is assumed.

The --delete option is a convenience option that runs the git update-ref --no-deref -d command on the specified tag removing it and its reflog (if it has one). Note that HEAD cannot be removed.

The --clear option clears all but the most recent (the @{0}) reflog entries from the reflog for the specified tag. It's equivalent to dropping all the higher numbered reflog entries.

The --drop option drops the specified reflog entry and requires the given tagname to have an @{n} suffix where n is the reflog entry number to be dropped. This is really just a convenience option that runs the appropriate git reflog delete command. Note that even dropping the ...@{0} entry when it's the last entry of a non-symbolic ref will NOT delete the ref itself (unless the ref was already somehow set to an invalid object hash); but dropping @{0} of a non-symbolic ref may have the side effect of removing some stale reflog entries that were present in the reflog.

Note that when combined with tg revert, a tag created by tg tag can be used to transfer TopGit branches. Simply create the tag, push it somewhere and then have the recipient run tg revert to recreate the TopGit branches. This may be helpful in situations where it's not feasible to push all the refs corresponding to the TopGit-controlled branches and their top-bases.

tg rebase

Provides a git rebase rerere auto continue function. It may be used as a drop-in replacement front-end for git rebase -m that automatically continues the rebase when git rerere information is sufficient to resolve all conflicts.

You have enabled git rerere haven't you?

If the -m or --merge option is not present then tg rebase will complain and not do anything.

When git rerere is enabled, previously resolved conflicts are remembered and can be automatically staged (see rerere.autoUpdate).

However, even with auto staging, git rebase still stops and requires an explicit git rebase --continue to keep going.

In the case where git rebase -m is being used to flatten history (such as after a tg export --collapse prior to a git format-patch), there's a good chance all conflicts have already been resolved during normal merge maintenance operations so there's no reason git rebase could not automatically continue, but there's no option to make it do so.

The tg rebase command provides a git rebase --auto-continue function.

All the same rebase options can be used (they are simply passed through to Git unchanged). However, the rerere.autoUpdate option is automatically temporarily enabled while running git rebase and should git rebase stop asking one to resolve and continue, but all conflicts have already been resolved and staged using rerere information, then git rebase --continue will be automatically run.

tg revert

Provides the ability to revert one or more TopGit branches and their dependencies to a previous state contained within a tag created using the tg tag command. In addition to the actual revert mode operation a list mode operation is also provided to examine a tag's ref contents.

The default mode (-l or --list) shows the state of one or more of the refs/branches stored in the tag data. When no refs are given on the command line, all refs in the tag data are shown. With the special ref name --heads then the indepedent heads contained in the tag data are shown. The --deps option shows the specified refs and all of their dependencies in a single list with no duplicates. The --rdeps option shows a display similar to tg summary --rdeps for each ref or all TopGit heads if no ref is given on the command line. The standard --no-short, --short=n etc. options may be used to override the default --short output. With --hash (or --hash-only) show only the hash in --list mode in which case the default is --no-short. The --hash option can be used much like the git rev-parse --verify command to extract a specific hash value out of a TopGit tag.

Note that unlike tg summary, here --heads actually does mean the git merge-base --independent heads of the stored refs from the tag data. To see only the independent TopGit topic branch heads stored in the tag data use the --topgit-heads option instead. The default for the --rdeps option is --topgit-heads but --heads can be given explicitly to change that. (Note that --heads-independent is accepted as an alias for --heads as well.)

The revert mode has three submodes, dry-run mode (-n or --dry-run), force mode (-f or --force) and interactive mode (-i or --interactive). If --dry-run (or -n) is given no ref updates will actually be performed but what would have been updated is shown instead. If --interactive (or -i) is given then the editor is invoked on an instruction sheet allowing manual selection of the refs to be updated before proceeding. Since revert is potentially a destructive operation, at least one of the submodes must be specified explicitly. If no refs are listed on the command line then all refs in the tag data are reverted. Otherwise the listed refs and all of their dependencies (unless --no-deps is given) are reverted. Unless --no-stash is given a new stash will be created using tg tag --stash (except, of course, in dry-run mode) just before actually performing the updates to facilitate recovery from accidents.

Both modes accept fully-qualified (i.e. starts with refs/) ref names as well as unqualified names (which will be assumed to be located under refs/heads/). In revert mode a tgish ref will always have both its refs/heads/ and refs/top-bases/ values included no matter how it's listed unless --no-deps is given and the ref is fully qualified (i.e. starts with refs/) or one or the other of its values was removed from the instruction sheet in interactive mode. In list mode a tgish ref will always have both its refs/heads/ and refs/top-bases/ values included only when using the --deps or --rdeps options.

The --tgish-only option excludes non-tgish refs (i.e. refs that do not have a refs/heads/<name>, refs/top-bases/<name> pair).

The --exclude option (which can be repeated) excludes specific refs. If the name given to --exclude is not fully-qualified (i.e. starts with refs/) then it will exclude both members of a tgish ref pair.

The --quiet (or -q) option may be used in revert mode to suppress non-dry-run ref change status messages.

The special tag name --stash (as well as with @{n} suffixes) can be used to refer to refs/tgstash.

The tg revert command supports tags of tags that contains TopGit refs. So, for example, if you do this:

tg tag newtag --all
git tag -f -a -m "tag the tag" newtag newtag

Then newtag will be a tag of a tag containing a TOPGIT REFS section. tg revert knows how to dereference the outermost tag to get to the next (and the next etc.) tag to find the TOPGIT REFS section so after the above sequence, the tag newtag can still be used successfully with tg revert.

NOTE: If HEAD points to a ref that is updated by a revert operation then NO WARNING whatsoever will be issued, but the index and working tree will always be left completely untouched (and the reflog for the pointed-to ref can always be used to find the previous value).

tg shell

Enter extended wayback machine mode.

The global -w <tgtag> option must be specified (but as a special case for the shell subcommand a <tgtag> destination of : may be used to get a shell with no wayback ref changes).

The "<tgtag>" value must be the name of a tag created by (or known to) tg tag. However, it may also have a : prefixed to it to indicate that it should prune (making it into a "pruning wayback tag"). Use of a "pruning wayback tag" results in a repository that contains exclusively those refs listed in the specified tag. Otherwise the wayback repository will just revert those refs while keeping the others untouched (the default behavior).

The wayback machine activates as normal for the specified destination but then a new ${SHELL:-/bin/sh} is spawned in a temporary non-bare repository directory that shares all the same objects from the repository but has its own copy of the ref namespace where the refs specified in the wayback destination have all been changed to have their wayback values.

If any arguments are given a POSIX shell will be spawned instead concatenating all the arguments together with a space and passing them to it via a -c option. If -q (or --quote) is given then each argument will first be separately "quoted" to protect it from the shell allowing something like this:

tg -w <tgtag> shell -q git for-each-ref --format="%(refname)"

to work without needing to manually add the extra level of quoting that would otherwise be required due to the parentheses.

Most of the repository configuration will be inherited, but some will be overridden for safety and for convenience. All "gc" activity within the wayback repository will be suppressed to avoid accidents (i.e. no auto gc will run and "gc" commands will complain and not run).

Override and/or bypass this safety protection at your own peril! Especially do not run the git prune plumbing command in the wayback repository! If you do so (or bypass any of the other safeties) be prepared for corruption and loss of data in the repository. Just don't do that in the first place!

Using git wayback-tag will show the tag used to enter the wayback machine. Using git wayback-updates will show ref changes that have occurred since the wayback tag was created (it will not show refs that have since been created unless a pruning wayback tag was used). Finally, git wayback-repository will show the home repository but so will git remote -v in the output displayed for the wayback remote.

The special wayback remote refers to the original repository and can be used to push ref changes back to it. Note, however, that all default push refspecs are disabled for safety and an explicit refspec will need to be used to do so.

Unlike the normal wayback machine mode, HEAD will be detached to a new commit with an empty tree that contains the message and author from the wayback tag used. This prevents ugly status displays while avoiding the need to checkout any files into the temporary working tree. The parent of this commit will, however, be set to the wayback tag's commit making it easy to access if desired.

Also unlike the normal wayback machine mode, there are no limitations on what can be done in the temporary repository. And since it will be non-bare and writable, commands that may not have been allowed in the original repository will work too.

When the shell spawned by this subcommand exits, the temporary wayback repository and all newly created objects and ref changes made in it, if any, will be lost. If work has been done in it that needs to be saved, it must be pushed somewhere (even if only back to the original repository using the special wayback remote).

Lastly there's the --directory option. If the --directory option is used the temporary "wayback repository" will be created at the specified location (which must either not exist or must be an empty directory -- no force option available this time as too many things could easily go wrong in that case). If the --directory option is used then the "wayback repository" will persist after tg shell completes allowing it to continue to be used! Be warned though, all the same warnings that apply to git clone --shared apply to such a repository. If it's created using a tgstash tag those warnings are especially salient. Use a single argument of either : (to just create with no output) or pwd (to show the full absolute path to the new "wayback repository") when using the --directory option if the sole purpose is just to create the wayback repository for use. Note that the --directory option must be listed as the first option after the shell subcommand name if used.

tg prev

Output the "previous" branch(es) in the patch series containing the current or named branch. The "previous" branch(es) being one step away by default.

Options:
-i show dependencies based on index instead of branch
-w show dependencies based on working tree instead of branch
-n <steps> take <steps> "previous" steps (default 1)
--all take as many "previous" steps as possible (aka -a)
--verbose show containing series name(s) (aka -v)

The -n option may also be given as --count or --count=<n>.

To list all dependencies of a branch see the --deps option of the tg info command.

See also NAVIGATION for full details on "previous" steps.

tg next

Output tne "next" branch(es) in the patch series containing the current or named branch. The "next" branch(es) being one step away by default.

Options:
-i show dependencies based on index instead of branch
-w show dependencies based on working tree instead of branch
-n <steps> take <steps> "next" steps (default 1)
--all take as many "next" steps as possible (aka -a)
--verbose show containing series name(s) (aka -v)

The -n option may also be given as --count or --count=<n>.

To list all dependents of a branch see the --dependents option of the tg info command.

See also NAVIGATION for full details on "next" steps.

tg migrate-bases

Transition top-bases from old location to new location.

Beginning with TopGit release 0.19.4, TopGit has the ability to store the top-bases refs in either the old ref/top-bases/... location or the new refs/heads/{top-bases}/... location. Starting with TopGit release 0.20.0, the default is the new location.

By storing the top-bases under heads, Git is less likely to complain when manipulating them, hosting providers are more likely to provide access to them and Git prevents them from pointing at anything other than a commit object. All in all a win for everyone.

TopGit attempts to automatically detect whether the new or old location is being used for the top-bases and just do the right thing. However, by explicitly setting the config value topgit.top-bases to either refs for the old location or heads for the new location the auto-detection can be bypassed. If no top-bases refs are present in the repository the default prior to TopGit release 0.20.0 is to use the old location but starting with TopGit release 0.20.0 the default is to use the new location.

The tg migrate-bases command may be used to migrate top-bases refs from the old location to the new location (or, by using the undocumented --reverse option, vice versa).

With few exceptions (tg create -r and tg revert), all top-bases refs (both local and remote refs) are expected to be stored in the same location (either new or old). A repository's current location for storing top-bases refs may be shown with the tg --top-bases command.

TODO: tg rename

IMPLEMENTATION

TopGit stores all the topic branches in the regular refs/heads/ namespace (so we recommend distinguishing them with the t/ prefix). Apart from that, TopGit also maintains a set of auxiliary refs in refs/top-*. Currently, only refs/top-bases/ is used, containing the current base of the given topic branch -- this is basically a merge of all the branches the topic branch depends on; it is updated during tg update and then merged to the topic branch, and it is the base of a patch generated from the topic branch by tg patch.

All the metadata is tracked within the source tree and history of the topic branch itself, in .top* files; these files are kept isolated within the topic branches during TopGit-controlled merges and are of course omitted during tg patch. The state of these files in base commits is undefined; look at them only in the topic branches themselves. Currently, two files are defined:

.topmsg:
Contains the description of the topic branch in a mail-like format, plus the author information, whatever Cc headers you choose or the post-three-dashes message. When mailing out your patch, basically only a few extra mail headers are inserted and then the patch itself is appended. Thus, as your patches evolve, you can record nuances like whether the particular patch should have To-list / Cc-maintainer or vice-versa and similar nuances, if your project is into that. From is prefilled from your current GIT_AUTHOR_IDENT; other headers can be prefilled from various optional topgit.* git config options.
.topdeps:
Contains the one-per-line list of branches this branch depends on, pre-seeded by tg create. A (continuously updated) merge of these branches will be the base of your topic branch.

IMPORTANT: DO NOT EDIT .topdeps MANUALLY!!! If you do so, you need to know exactly what you are doing, since this file must stay in sync with the Git history information, otherwise very bad things will happen.

TopGit also automagically installs a bunch of custom commit-related hooks that will verify whether you are committing the .top* files in a sane state. It will add the hooks to separate files within the hooks/ subdirectory, and merely insert calls to them to the appropriate hooks and make them executable (but will make sure the original hook's code is not called if the hook was not executable beforehand).

Another automagically installed piece is a .git/info/attributes specifier for an ours merge strategy for the files .topmsg and .topdeps, and the (intuitive) ours merge strategy definition in .git/config.

REMOTE HANDLING

There are two remaining issues with accessing topic branches in remote repositories:

  1. Referring to remote topic branches from your local repository
  2. Developing some of the remote topic branches locally

There are two somewhat contradictory design considerations here:

  1. Hacking on multiple independent TopGit remotes in a single repository
  2. Having a self-contained topic system in local refs space

To us, (a) does not appear to be very convincing, while (b) is quite desirable for git-log topic etc. working, and increased conceptual simplicity.

Thus, we choose to instantiate all the topic branches of given remote locally; this is performed by tg remote --populate. tg update will also check if a branch can be updated from its corresponding remote branch. The logic needs to be somewhat involved if we are to "do the right thing". First, we update the base, handling the remote branch as if it was the first dependency; thus, conflict resolutions made in the remote branch will be carried over to our local base automagically. Then, the base is merged into the remote branch and the result is merged to the local branch -- again, to carry over remote conflict resolutions. In the future, this order might be adjustable on a per-update basis, in case local changes happen to be diverging more than the remote ones. (See the details in The Update Process for more in depth coverage.)

All commands by default refer to the remote that tg remote --populate was called on the last time (stored in the topgit.remote git configuration variable). You can manually run any command with a different base remote by passing -r REMOTE before the subcommand name or passing -u before the subcommand to run without one.

TESTING TOPGIT

Running the TopGit test suite only requires POSIX compatibile utilities (just a POSIX compatibile make will do) AND a perl binary.

It is not necessary to install TopGit in order to run the TopGit test suite.

To run the TopGit test suite, simply execute this from the top-level of a TopGit checkout or expanded release tarball:

make test

Yup, that's it. But you're probably thinking, "Why have a whole section just to say 'run make test'?" Am I right?

The simple make test command produces a lot of output and while it is summarized at the end there's a better way.

Do you have the prove utility available? You need perl to run the tests and prove comes with perl so you almost cerainly do.

Try running the tests like so:

make DEFAULT_TEST_TARGET=prove test

(For reference, the default value of DEFAULT_TEST_TARGET is test which can be used to override a setting that's been altered using the instructions shown later on below.)

If that works (you can interrupt it with Ctrl-C), try this next:

make DEFAULT_TEST_TARGET=prove TESTLIB_PROVE_OPTS="-j 4 --timer" test

If that one works (again, you can interrupt it with Ctrl-C) that may end up being the keeper for running the tests.

However, if you don't have prove for some reason even though you do have perl, there's still an alternative for briefer output. Try this:

make TESTLIB_TEST_OPTS=-q test

Much of the normal testing output will be suppressed and there's still a summary at the end. If you're stuck with this version but your make supports parallel operation (the -j <n>) option, then you might try this:

make -j 4 TESTLIB_TEST_OPTS=-q test

If your make does support the parallel -j option but still seems to be only running one test at a time try it like this instead:

make TESTLIB_MAKE_OPTS="-j 4" TESTLIB_TEST_OPTS=-q test

The difference is that make -j 4 relies on make to properly pass down the parallel job option all the way down to the sub-make that runs the individual tests when not using prove. Putting the options in TESTLIB_MAKE_OPTS passes them directly to that (and only that) particular invocation of make.

The final bit of advice for running the tests is that any of those make variable settings can be enabled by default in a top-level config.mak file.

For example, to make the prove -j 4 --timer (my personal favorite) the default when running the tests, add these lines (creating the file if it does not already exist) to the config.mak file located in the top-level of the TopGit checkout (or expanded release tarball):

# config.mak file
# comments are allowed (if preceded by '#')
# so are blank lines

DEFAULT_TEST_TARGET = prove
TESTLIB_PROVE_OPTS = -j 4 --timer
#TESTLIB_TEST_OPTS = --color # force colorized test output

Now simply doing make test will use those options by default.

There is copious documentation on the testing library and other options in the various README files located in the t subdirectory. The Makefile.mak file in the t subdirectory contains plenty of comments about possible makefile variable settings as well.

TECHNICAL

A familiarity with the terms in the GLOSSARY is helpful for understanding the content of this section. See also the IMPLEMENTATION section.

The Update Process

When a branch is "updated" using the tg update command the following steps are taken:

  1. The branch and all of its dependencies (and theirs recursively) are checked to see which ones are out-of-date. See glossary.
  2. Each of the branch's direct dependencies (i.e. they are listed in the branch's .topdeps file) which is out of date is updated before proceeding (yup, this is a recursive process).
  3. Each of the branch's direct dependencies (i.e. they are listed in the branch's .topdeps file) that was updated in the previous step is now merged into the branch's corresponding base. If a remote is involved, and the branch's corresponding base does NOT contain the remote branch's corresponding base that remote base is also merged into the branch's base at this time as well (it will be the first item merged into the branch's base).
  4. If the branch has a corresponding remote branch and the branch does not already contain it, the branch's base (which was possibly already updated in step (3) to contain the remote branch's base but not the remote branch itself) is merged into the remote branch on a detached HEAD. Yup, this step can be a bit confusing and no, the updated base from step (3) has not yet been merged into the branch itself yet either. If there is no remote branch this step does not apply. Using a detached HEAD allows the contents of the base to be merged into the remote branch without actually perturbing the base's or remote branch's refs.
  5. If there is a remote branch present then use the result of step (4) otherwise use the branch's base and merge that into the branch itself.

That's it! Simple, right? ;)

Unless the auto stash option has been disabled (see no undo, tg update and tg tag), a copy of all the old refs values will be stashed away immediately after step (1) before starting step (2), but only if anything is actually found to be out-of-date.

Merge Strategies

The tg update command regularly performs merges while executing an update operation. In order to speed things up, it attempts to do in-index merges where possible. It accomplishes this by using a separate, temporary index file and the git read-tree -m --aggressive command possibly assisted by the git merge-index and git merge-file commands. This combination may be repeated more than once to perform an octopus in-index merge. If this fails, the files are checked out and a normal git merge three-way merge is performed (possibly multiple times). If the normal git merge fails then user intervention is required to resolve the merge conflict(s) and continue.

Since the tg annihilate, tg create and tg depend add commands may end up running the tg update machinery behind the scenes to complete their operation they may also result in any of these merge strategies being used.

In addition to the normal Git merge strategies (if the in-index merging fails), there are four possible TopGit merge strategies that may be shown. Since they all involve use of the git read-tree -m --aggressive command they are all variations of a "trivial aggressive" merge. The "trivial" part because all of the merges done by git read-tree -m are described as "trivial" and the "aggressive" part because the --aggressive option is always used.

  1. "trivial aggressive"
    Only two heads were involved and all merging was completed by the git read-tree -m --aggressive command.
  2. "trivial aggressive automatic"
    Only two heads were involved but after the git read-tree -m --aggressive command completed there were still unresolved items and git merge-index had to be run (using the tg index-merge-one-file driver) which ultimately ran git merge-file at least once to perform a simple automatic three-way merge. Hence the "automatic" description and the "Auto-merging ..." output line(s).
  3. "trivial aggressive octopus"
    This is the same as a "trivial aggressive" merge except that more than two heads were involved and after merging the first two heads, the git read-tree -m --aggressive step was repeated again on the result for each additional head. All merging was completed via multiple git read-tree -m --aggressive commands only. This beast is relatively rare in the wild.
  4. "trivial aggressive automatic octopus"
    This is very similar to the "trivial aggressive octopus" except that at least one of the git read-tree -m --aggressive commands left unresolved items that were handled the same way as the "trivial aggressive automatic" strategy. This species is commonly seen in the wild.

GLOSSARY

.topmsg
Version-controlled file stored at the root level of each TopGit branch that contains the patch header for a TopGit branch. See also IMPLEMENTATION.
.topdeps
Version-controlled file stored at the root level of each TopGit branch that lists the branch's dependencies one per line omitting the leading refs/heads/ part. See also IMPLEMENTATION.
branch containment
Given two Git commit identifiers (e.g. hashes) C1 and C2, commit C1 "contains" commit C2 if either they are the same commit or C2 can be reached from C1 by following one or more parent links from C1 (perhaps via one or more intermediate commits along the way). In other words, if C1 contains C2 then C2 is an ancestor of C1 or conversely C1 is a descendant of C2. Since a TopGit branch name is also the name of a Git branch (something located under the refs/heads Git namespace) and similarly for a TopGit base, they can both be resolved to a Git commit identifier and then participate in a branch containment test. An easy mnemonic for this is "children contain the genes of their parents."
BRE pattern
A Basic Regular Expression (BRE) pattern. These are older style regular expressions but have the advantage that all characters other than \, ., * and [ automatically match themselves without need for backslash quoting (well actually, ^ and $ are special at the beginning and end respectively but otherwise match themselves).
contains
See branch containment.
ERE pattern
An Extended Regular Expression (ERE) pattern. These are newer style regular expressions where all the regular expression "operator" characters "operate" when NOT preceded by a backslash and are turned into normal characters with a \. The backreference atom, however, may not work, but ?, + and | "operators" do; unlike BREs.
TopGit
Excellent system for managing a history of changes to one or more possibly interrelated patches.
TopGit branch
A Git branch that has an associated TopGit base. Conceptually it represents a single patch that is the difference between the associated TopGit base and the TopGit branch. In other words git diff-tree <TopGit base> <TopGit branch> except that any .topdeps and/or .topmsg files are excluded from the result and the contents of the .topmsg file from the TopGit branch is prefixed to the result.
TopGit bare branch
A Git branch whose tree does NOT contain any .topdeps or .topmsg entries at the top-level of the tree. It does always have an associated "TopGit base" ref (otherwise it would not be a "TopGit" branch). See also BARE BRANCHES.
bare branch
In TopGit context, "bare branch" almost always refers to a "TopGit bare branch" and should be understood to mean such even if the leading "TopGit" has been left off.
TopGit base

A Git branch that records the base upon which a TopGit branch's single conceptual "patch" is built. The name of the Git branch is derived from the TopGit branch name by stripping off the leading refs/heads/ and appending the correct prefix where all TopGit bases are stored (typically either refs/top-bases/ or refs/heads/{top-bases}/ -- the prefix for any given repository can be shown by using the tg --top-bases command and updated using the tg migrate-bases command).

All of a TopGit branch's dependencies are merged into the corresponding TopGit base during a tg update of a branch.

base
See TopGit base.
TopGit [PATCH] branch
A TopGit branch whose subject starts with [PATCH]. By convention these TopGit branches contain a single patch (equivalent to a single patch file) and have at least one dependency (i.e. their .topdeps files are never empty).
TopGit [BASE] branch
A TopGit branch whose subject starts with [BASE]. By convention these TopGit branches do not actually contain any changes and their .topdeps files are empty. They are used to control a base dependency that another set of branches depends on. Sometimes these are named [RELEASE] instead because the base dependency they represent is actually the formal release of something.
TopGit [STAGE] branch
A TopGit branch whose subject starts with [STAGE]. By convention these TopGit branches do not actually contain any changes of their own but do have one or (typically) more dependencies in their .topdeps file. These branches are used to bring together one or (typically) more independent TopGit [PATCH] branches into a single branch so that testing and/or evaluation can be performed on the result.
merge conflict
When merging two (or more) heads that touch the same lines in the file but in different ways the result is a merge conflict that requires manual intervention. If a merge conflict occurs with more than two heads (an octopus merge) it's generally replaced by multiple three-way merges so that by the time a user sees a merge conflict needing manual resolution, there will be only two heads involved.
merge strategy
A Git merge strategy (see the "MERGE STRATEGIES" section of git help merge) or one of the TopGit merge strategies used to merge two or more heads.
TopGit merge strategy
See the Merge Strategies section above for details but basically these are just in-index merges done using the git read-tree -m --aggressive command one or more times possibily assisted by the git merge-index and the git merge-file commands.
next branch
In TopGit context the "next" branch refers to the branch that corresponds to the next (aka following) patch in an ordered (aka linearized) list of patches created by exporting the TopGit branches in patch application order.
octopus merge
A merge involving more than two heads. Note that if there are less than three independent heads the resulting merge that started out as an octopus will end up not actually being an octopus after all.
out-of-date branch

A TopGit branch is considered to be "out-of-date" when ANY of the following are true:

  1. The TopGit branch does NOT contain its corresponding base.
  2. The TopGit branch does NOT contain its corresponding remote branch (there may not be a remote branch in which case this does not apply)
  3. The TopGit branch's base does NOT contain its corresponding remote branch's base (there may not be a remote branch in which case this does not apply)
  4. Any of the TopGit branches listed in the branch's .topdeps file are NOT contained by the branch. (See "branch containment" above.)
  5. Any of the TopGit branches listed in the branch's .topdeps file are out-of-date.

Note that if a remote branch is present and is NOT out-of-date then it will contain its own base and (c) is mostly redundant.

previous branch
In TopGit context the "previous" (or "prev") branch refers to the branch that corresponds to the previous (aka preceding) patch in an ordered (aka linearized) list of patches created by exporting the TopGit branches in patch application order.
remote TopGit branch
A Git branch with the same branch name as a TopGit branch but living under refs/remotes/<some remote>/ instead of just refs/heads/.
remote TopGit base
The TopGit base branch corresponding to a remote TopGit branch, which lives under refs/remotes/ somewhere (depending on what the output of tg --top-bases is for that remote).
three-way merge
A three-way merge takes a common base and two heads (call them A and B) and creates a new file that is the common base plus all of the changes made between the common base and head A AND all of the changes made between the common base and head B. The technique used to accomplish this is called a "merge strategy".

REFERENCES

The following references are useful to understand the development of topgit and its subcommands.

THIRD-PARTY SOFTWARE

The following software understands TopGit branches:

IMPORTANT: Magit requires its topgit mode to be enabled first, as described in its documentation, in the "Activating extensions" subsection. If this is not done, it will not push TopGit branches correctly, so it's important to enable it even if you plan to mostly use TopGit from the command line.