Perform a merge between two branches incrementally. If conflicts are encountered, figure out exactly which pairs of commits conflict, and present the user with one pairwise conflict at a time for resolution.
git-imerge has two primary design goals:
- Reduce the pain of resolving merge conflicts to its unavoidable minimum, by finding and presenting the smallest possible conflicts: those between the changes introduced by one commit from each branch.
- Allow a merge to be saved, tested, interrupted, published, and collaborated on while it is in progress.
I think that it is easiest to understand the concept of incremental
merging visually, and therefore I recommend the video of my
git-imerge presentation from the GitMerge 2013 conference (20 min)
as a good place to start. The full slides for that talk are available
in this repository under doc/presentations/GitMerge-2013. At the
same conference, I was interviewed about git-imerge by Thomas
Ferris Nicolaisen for his GitMinutes Podcast #12.
To learn how to use the git-imerge tool itself, I suggest the blog
article git-imerge: A Practical Introduction and also typing
git-imerge --help and git-imerge SUBCOMMAND --help. If you
want more information, the theory and benefits of incremental merging
are described in minute detail in a series of blog articles [1], as
are the benefits of retaining history when doing a rebase [2].
Multiple incremental merges can be in progress at the same time. Each
incremental merge has a name, and its progress is recorded in the Git
repository as references under refs/imerge/NAME. The current
state of an incremental merge can be visualized using the diagram
command.
An incremental merge can be interrupted and resumed arbitrarily, or even pushed to a server to allow somebody else to work on it.
git-imerge is experimental! If it breaks, you get to keep the pieces. Feedback and bug reports are welcome!
git-imerge requires:
A Python interpreter; either
- Python 2.x, version 2.6 or later. If you are using Python
2.6.x, then you have to install the
argparsemodule yourself, as it was only added to the standard library in Python 2.7. - Python 3.x, version 3.3 or later.
The script tries to use a Python interpreter called
pythonin yourPATH. If your Python interpreter has a different name or is not in yourPATH, please adjust the first line of the script accordingly.- Python 2.x, version 2.6 or later. If you are using Python
2.6.x, then you have to install the
A recent version of Git.
To start a merge or rebase operation using git-imerge, you use
commands that are similar to the corresponding git commands:
git command |
git-imerge equivalent |
|---|---|
git merge BRANCH |
git-imerge merge BRANCH |
git rebase BRANCH |
git-imerge rebase BRANCH |
For more flexibility, you can start an incremental merge using git
imerge start:
git-imerge start --name=NAME --goal=GOAL --first-parent BRANCH
where
NAME- is the name for this merge (and also the default name of the branch to which the results will be saved).
GOALdescribes how you want to simplify the results (see next- section).
After the incremental merge is started, you will be presented with any
conflicts that have to be resolved. The basic procedure is similar
to performing an incremental merge using git:
while not done:
<fix the conflict that is presented to you>
<"git add" the files that you changed>
git-imerge continue
When you have resolved all of the conflicts, you finish the incremental merge by typing:
git-imerge finish
That should be enough to get you going. All of these subcommands have additional options; to learn about them type:
git-imerge --help git-imerge SUBCMD --help
When the incremental merge is finished, you can simplify its results
in various ways before recording it in your project's permanent
history by using either the finish or simplify command. The
"goal" of the incremental merge can be one of the following:
mergekeep only a simple merge of the second branch into the first branch, discarding all intermediate merges. The end result is similar to what you would get from
git checkout BRANCH1 git merge BRANCH2
rebasekeep the versions of the commits from the second branch rebased onto the first branch. The end result is similar to what you would get from
git checkout BRANCH2 git rebase BRANCH1
rebase-with-historylike
rebase, except that it retains the old versions of the rebased commits in the history. It is equivalent to merging the commits fromBRANCH2intoBRANCH1, one commit at a time. In other words, it transforms this:o---o---o---o BRANCH1 \ A---B---C---D BRANCH2into this:
o---o---o---o---A'--B'--C'--D' NEW_BRANCH \ / / / / --------A---B---C---DIt is safe to rebase an already-published branch using this approach. See [2] for more information.
full- don't simplify the incremental merge at all: do all of the intermediate merges and retain them all in the permanent history.
git-imerge is released as open-source software under the GNU
General Public License (GPL), version 2 or later.
| [2] | (1, 2) |