Git annex

Warning: GitLab has completely removed in GitLab 9.0 (2017/03/22). Read through the migration guide from git-annex to Git LFS.

The biggest limitation of Git, compared to some older centralized version control systems has been the maximum size of the repositories.

The general recommendation is to not have Git repositories larger than 1GB to preserve performance. Although GitLab has no limit (some repositories in GitLab are over 50GB!), we subscribe to the advice to keep repositories as small as you can.

Not being able to version control large binaries is a big problem for many larger organizations. Videos, photos, audio, compiled binaries, and many other types of files are too large. As a workaround, people keep artwork-in-progress in a Dropbox folder and only check in the final result. This results in using outdated files, not having a complete history, and increases the risk of losing work.

This problem is solved in GitLab Enterprise Edition by integrating the git-annex application.

git-annex allows managing large binaries with Git without checking the contents into Git. You check-in only a symlink that contains the SHA-1 of the large binary. If you need the large binary, you can sync it from the GitLab server over rsync, a very fast file copying tool.

GitLab git-annex Configuration

git-annex is disabled by default in GitLab. Below you will find the configuration options required to enable it.

Requirements

git-annex needs to be installed both on the server and the client-side.

For Debian-like systems (for example, Debian and Ubuntu) this can be achieved by running:

sudo apt-get update && sudo apt-get install git-annex

For RedHat-like systems (for example, CentOS and RHEL) this can be achieved by running:

sudo yum install epel-release && sudo yum install git-annex

Configuration for Omnibus packages

For Omnibus GitLab packages, only one configuration setting is needed. The Omnibus package will internally set the correct options in all locations.

In /etc/gitlab/gitlab.rb add the following line:
```
gitlab_shell['git_annex_enabled'] = true
```
Save the file and reconfigure GitLab for the changes to take effect.

Configuration for installations from source

There are 2 settings to enable git-annex on your GitLab server.

One is located in config/gitlab.yml of the GitLab repository and the other one is located in config.yml of GitLab Shell.

In config/gitlab.yml add or edit the following lines:
```
gitlab_shell:
  git_annex_enabled: true
```
In config.yml of GitLab Shell add or edit the following lines:
```
git_annex_enabled: true
```
Save the files and restart GitLab for the changes to take effect.

Using GitLab git-annex

Note: Your Git remotes must be using the SSH protocol, not HTTP(S).

Here is an example workflow of uploading a very large file and then checking it into your Git repository:

git clone [email protected]:group/project.git

git annex init 'My Laptop'       # initialize the annex project and give an optional description
cp ~/tmp/debian.iso ./           # copy a large file into the current directory
git annex add debian.iso         # add the large file to git annex
git commit -am "Add Debian iso"  # commit the file metadata
git annex sync --content         # sync the Git repo and large file to the GitLab server

The output should look like this:

commit
On branch master
Your branch is ahead of 'origin/master' by 1 commit.
  (use "git push" to publish your local commits)
nothing to commit, working tree clean
ok
pull origin
remote: Counting objects: 5, done.
remote: Compressing objects: 100% (4/4), done.
remote: Total 5 (delta 2), reused 0 (delta 0)
Unpacking objects: 100% (5/5), done.
From example.com:group/project
   497842b..5162f80  git-annex  -> origin/git-annex
ok
(merging origin/git-annex into git-annex...)
(recording state in git...)
copy debian.iso (checking origin...) (to origin...)
SHA256E-s26214400--8092b3d482fb1b7a5cf28c43bc1425c8f2d380e86869c0686c49aa7b0f086ab2.iso
     26,214,400 100%  638.88kB/s    0:00:40 (xfr#1, to-chk=0/1)
ok
pull origin
ok
(recording state in git...)
push origin
Counting objects: 15, done.
Delta compression using up to 4 threads.
Compressing objects: 100% (13/13), done.
Writing objects: 100% (15/15), 1.64 KiB | 0 bytes/s, done.
Total 15 (delta 1), reused 0 (delta 0)
To example.com:group/project.git
 * [new branch]      git-annex -> synced/git-annex
 * [new branch]      master -> synced/master
ok

Your files can be found in the master branch, but you'll notice that there are more branches created by the annex sync command.

Git Annex will also create a new directory at .git/annex/ and will record the tracked files in the .git/config file. The files you assign to be tracked with git-annex will not affect the existing .git/config records. The files are turned into symbolic links that point to data in .git/annex/objects/.

The debian.iso file in the example will contain the symbolic link:

.git/annex/objects/ZW/1k/SHA256E-s82701--6384039733b5035b559efd5a2e25a493ab6e09aabfd5162cc03f6f0ec238429d.png/SHA256E-s82701--6384039733b5035b559efd5a2e25a493ab6e09aabfd5162cc03f6f0ec238429d.iso

Use git annex info to retrieve the information about the local copy of your repository.

Downloading a single large file is also very simple:

git clone [email protected]:group/project.git

git annex sync             # sync Git branches but not the large file
git annex get debian.iso   # download the large file

To download all files:

git clone [email protected]:group/project.git

git annex sync --content  # sync Git branches and download all the large files

By using git-annex without GitLab, anyone that can access the server can also access the files of all projects, but GitLab Annex ensures that you can only access files of projects you have access to (developer, maintainer, or owner role).

How it works

Internally GitLab uses GitLab Shell to handle SSH access and this was a great integration point for git-annex. There is a setting in GitLab Shell so you can disable GitLab Annex support if you want to.

Troubleshooting tips

Differences in the version of git-annex on the GitLab server and on local machines can cause git-annex to raise unpredicted warnings and errors.

Consult the Annex upgrade page for more information about the differences between versions. You can find out which version is installed on your server by navigating to https://pkgs.org/download/git-annex and searching for your distribution.

Although there is no general guide for git-annex errors, there are a few tips on how to go around the warnings.

`git-annex-shell: Not a git-annex or gcrypt repository`

This warning can appear on the initial git annex sync --content and is caused by differences in git-annex-shell. You can read more about it in this git-annex issue.

One important thing to note is that despite the warning, the sync succeeds and the files are pushed to the GitLab repository.

If you get hit by this, you can run the following command inside the repository that the warning was raised:

git config remote.origin.annex-ignore false

Consecutive runs of git annex sync --content should not produce this warning and the output should look like this:

commit  ok
pull origin
ok
pull origin
ok
push origin