Checking large binary files into a source repository (Git or otherwise) is a bad idea because repository size quickly becomes unreasonable. Even if the instantaneous working tree stays manageable, preserving repository integrity requires all binary files in the entire project history, which given the typically poor compression of binary diffs, implies that the repository size will become impractically large. Some people recommend checking binaries into different repositories or even not versioning them at all, but these are not satisfying solutions for most workflows.
- clones of the source repository are small and fast because no binaries are transferred, yet fully functional (unlike
git clone --depth)
git-fatsupports the same workflow for large binaries and traditionally versioned files, but internally manages the "fat" files separately
git-bisectworks properly even when versions of the binary files change over time
- selective control of which large files to pull into the local store
- local fat object stores can be shared between multiple clones, even by different users
- can easily support fat object stores distributed across multiple hosts
- depends only on stock Python and rsync
- git-annex is a far more comprehensive solution, but with less transparent workflow and with more dependencies.
- git-media adopts a similar approach to
git-fat, but with a different synchronization philosophy and with many Ruby dependencies.
Installation and configuration
git-fat in your
.gitattributes to regard any desired extensions as fat files.
$ cat >> .gitattributes *.png filter=fat -text *.jpg filter=fat -text *.gz filter=fat -text ^D
git fat init to activate the extension. Now add and commit as usual.
Matched files will be transparently stored externally, but will appear
complete in the working tree.
Set a remote store for the fat objects by editing
[rsync] remote = your.remote-host.org:/share/fat-store
This file should typically be committed to the repository so that others will automatically have their remote set. This remote address can use any protocol supported by rsync.
Most users will configure it to use remote ssh in a directory with shared
access. To do this, set the
sshport variables in
configuration file. For example, to use rsync with ssh, with the default
port (22) and authenticate with the user "fat", your configuration would
look like this:
[rsync] remote = your.remote-host.org:/share/fat-store sshuser = fat
A worked example
Before we start, let's turn on verbose reporting so we can see what's
happening. Without this environment variable, all the output lines
git-fat will not be shown.
$ export GIT_FAT_VERBOSE=1
First, we create a repository and configure it for use with
$ git init repo Initialized empty Git repository in /tmp/repo/.git/ $ cd repo $ git fat init $ cat > .gitfat [rsync] remote = localhost:/tmp/fat-store $ mkdir -p /tmp/fat-store # make sure the remote directory exists $ echo '*.gz filter=fat -text' > .gitattributes $ git add .gitfat .gitattributes $ git commit -m'Initial repository' [master (root-commit) eb7facb] Initial repository 2 files changed, 3 insertions(+) create mode 100644 .gitattributes create mode 100644 .gitfat
Now we add a binary file whose name matches the pattern we set in
$ curl https://nodeload.github.com/jedbrown/git-fat/tar.gz/master -o master.tar.gz % Total % Received % Xferd Average Speed Time Time Time Current Dload Upload Total Spent Left Speed 100 6449 100 6449 0 0 7741 0 --:--:-- --:--:-- --:--:-- 9786 $ git add master.tar.gz git-fat filter-clean: caching to /tmp/repo/.git/fat/objects/b3489819f81603b4c04e8ed134b80bace0810324 $ git commit -m'Added master.tar.gz' [master b85a96f] Added master.tar.gz git-fat filter-clean: caching to /tmp/repo/.git/fat/objects/b3489819f81603b4c04e8ed134b80bace0810324 1 file changed, 1 insertion(+) create mode 100644 master.tar.gz
The patch itself is very simple and does not include the binary.
$ git show --pretty=oneline HEAD 918063043a6156172c2ad66478c6edd5c7df0217 Add master.tar.gz diff --git a/master.tar.gz b/master.tar.gz new file mode 100644 index 0000000..12f7d52 --- /dev/null +++ b/master.tar.gz @@ -0,0 +1 @@ +#$# git-fat 1f218834a137f7b185b498924e7a030008aee2ae
Pushing fat files
Now let's push our fat files using the rsync configuration that we set up earlier.
$ git fat push Pushing to localhost:/tmp/fat-store building file list ... 1 file to consider sent 61 bytes received 12 bytes 48.67 bytes/sec total size is 6449 speedup is 88.34
We might normally set a remote now and push the git repository.
Cloning and pulling
Now let's look at what happens when we clone.
$ cd .. $ git clone repo repo2 Cloning into 'repo2'... done. $ cd repo2 $ git fat init # don't forget $ ls -l # file is just a placeholder total 4 -rw-r--r-- 1 jed users 53 Nov 25 22:42 master.tar.gz $ cat master.tar.gz # holds the SHA1 of the file #$# git-fat 1f218834a137f7b185b498924e7a030008aee2ae
We can always get a summary of what fat objects are missing in our local cache.
Orphan objects: 1f218834a137f7b185b498924e7a030008aee2ae
Now get any objects referenced by our current
HEAD. This command also
--all option to pull full history, or a revision to pull
$ git fat pull receiving file list ... 1 file to consider 1f218834a137f7b185b498924e7a030008aee2ae 6449 100% 6.15MB/s 0:00:00 (xfer#1, to-check=0/1) sent 30 bytes received 6558 bytes 4392.00 bytes/sec total size is 6449 speedup is 0.98 Restoring 1f218834a137f7b185b498924e7a030008aee2ae -> master.tar.gz git-fat filter-smudge: restoring from /tmp/repo2/.git/fat/objects/1f218834a137f7b185b498924e7a030008aee2ae
Everything is in place
$ git status git-fat filter-clean: caching to /tmp/repo2/.git/fat/objects/1f218834a137f7b185b498924e7a030008aee2ae # On branch master nothing to commit, working directory clean $ ls -l # recovered the full file total 8 -rw-r--r-- 1 jed users 6449 Nov 25 17:10 master.tar.gz
- Set the "fat" file types in
- Use normal git commands to interact with the repository without thinking about what files are fat and non-fat. The fat files will be treated specially.
- Synchronize fat files with
git fat pushand
git fat pull.
Retroactive import using
git filter-branch [Experimental]
Sometimes large objects were added to a repository by accident or for
lack of a better place to put them. If you are willing to rewrite
history, forcing everyone to reclone, you can retroactively manage those
git fat. Be sure that you understand the consequences of
git filter-branch before attempting this. This feature is experimental
and irreversible, so be doubly careful with backups.
Step 1: Locate the fat files
git fat find THRESH_BYTES > fat-files and inspect
an editor. Lines will be sorted by the maximum object size that has been
at each path, and look like
something.big filter=fat -text # 8154677 1
where the first number after the
# is the number of bytes and the
second number is the number of modifications that path has seen. You
will normally filter out some of these paths using grep and/or an
editor. When satisfied, remove the ends of the lines (including the
and append to
.gitattributes. It's best to
git add .gitattributes and commit
at this time (likely enrolling some extant files into
/tmp/fat-filter-files and edit to remove
everything after the file name (e.g.,
sed s/ \+filter=fat.*$//).
Currently, this may only contain exact paths relative to the root of the
repository. Finally, run
git filter-branch --index-filter \ 'git fat index-filter /tmp/fat-filter-files --manage-gitattributes' \ --tag-name-filter cat -- --all
(You can remove the
--manage-gitattributes option if you don't want to
append all the files being enrolled in
git fat to
however, future users would need to use
.git/info/attributes to have
git fat fileters run.)
When this finishes, inspect to see if everything is in order and follow
Checklist for Shrinking a Repository
git filter-branch man page, typically
git clone file:///path/to/repo. Be sure to
git fat push from the original
See the script
test-retroactive.sh for an example of cleaning.
The actual binary files are stored in
.git/objects nice and small.
$ du -bs .git/objects 2212 .git/objects/ $ ls -l .git/fat/objects # This is where the file actually goes, but that's not important total 8 -rw------- 1 jed users 6449 Nov 25 17:01 1f218834a137f7b185b498924e7a030008aee2ae
If you have multiple clones that access the same filesystem, you can make
.git/fat/objects a symlink to a common location, in which case all content
will be available in all repositories without extra copies. You still need to
git fat push to make it available to others.
- Allow pulling and pushing only select files
- Relate orphan objects to file system
- Put some more useful message in smudged (working tree) version of missing files.
- More friendly configuration for multiple fat remotes
- Make commands safer in presence of a dirty tree.
- Private setting of a different remote.
- Gracefully handle unmanaged files when the filter is called (either legacy files or files matching the pattern that should some reason not be treated as fat).