git-mirror is a tool to keep multiple git repositories of the same project in sync. Whenever something is pushed to any repository, the commits will immediately be forwarded to all the others. The tool assumes to run on a server hosting one of these repositories - so there has to be at least one you can control. A typical use-case would be your own gitolite installation, that you want to keep in sync with GitHub.
This describes how you set up git-mirror on a server running gitolite. For other
git hosting software, please consult the respective documentation on adding git
hooks. I will assume that gitolite is installed to /home/git/gitolite, that
the repositories are sitting in /home/git/repositories, and that git-mirror
has been cloned to /home/git/git-mirror.
First of all, you need to create a file called git-mirror.conf in the
git-mirror directory. For now, it only needs to contain a single line:
mail-sender = [email protected]
We will also need to add hooks to the git repositories you want to sync. The
easiest way to manage these hooks is to put them into your gitolite-admin
repository, so enable the following line in /home/git/.gitolite.rc:
LOCAL_CODE => "$rc{GL_ADMIN_BASE}/local",
Make sure you read the security note concerning this configuration.
Furthermore, uncomment the repo-specific-hooks line in the rc file or add it
to the ENABLE list if it doesn't exist.
Now add a file called local/hooks/repo-specific/git-mirror to your
gitolite-admin repository, make it executable, and give it the following
content:
#!/bin/sh
exec ~/git-mirror/githook.py
For every repository you want to be synced, you can enable the hook by adding
the following line to its configuration in conf/gitolite.conf:
option hook.post-receive = git-mirror
(If you need multiple hooks here, you can separate them by spaces.)
Finally, you need to tell git-mirror where to sync incoming changes to this
repository to. Add a block like the following to git-mirror.conf:
[repo-name]
owner = [email protected]
local = /home/git/repositories/repo-name.git
deploy-key = ssh-key
mirror-a = [email protected]:repo-name.git
mirror-b = [email protected]:the-repo.git
Here, local has to be set to the path where the repository is stored
locally. deploy-key is the name of the SSH key used for pushing the changes
to other repositories. owner is the e-mail-address that errors occurring
during synchronization are sent to. And finally, the URLs to push to are given
by mirror-<something>. If these other servers also run gitolite and have a
symmetric setup, then no matter where a change is pushed, git-mirror will
forward it to all the other repositories.
If one of the to-be-synced repositories is on GitHub, you can obviously not use the procedure above to sync changes that are arriving at GitHub, to the other repositories. Instead, we will use a webhook, such that GitHub tells your server that a change happened, and then your server can pull the changes to its local repository and synchronize all the others. This assumes that the server running the webhook also hosts one of the copies of the git repository.
First of all, you will have to configure your webserver to run webhook.py as
CGI script. Consult the webserver documentation for more details.
Secondly, webhook.py needs to be able to find the main git-mirror scripts,
and it needs to be able to execute them as the git user. For the first
point, open webhook.py and change webhook_core to point to the file
webhook-core.py in your git-mirror clone. If your installation matches the
paths I used above, that should already be the case. For the second point,
webhook.py is using sudo to elevate its privileges. You need to tell
sudo that this is all right, by creating a file
/etc/sudoers.d/git-mirror with content:
www-data ALL=(git) NOPASSWD: /home/git/git-mirror/webhook-core.py
Now, if you visit https://example.com/git-mirror/webhook.py (replace with
your URL), the script should run and tell you Repository missing or not found..
The next step is to add this as a webhook to the GitHub repository you want to
sync with, to create a fresh SSH key and configure it as deployment key for the
repository, and to configure git-mirror accordingly. For additional security,
one should also configure a shared HMAC secret, such that the webhook can verify
that the data indeed comes from GitHub. On the git-mirror side, the HMAC secret
is configured with the hmac-secret repository option.
To make your job easier, there is a script github-add-hooks.py that can do
all this for you. It assumes that the repository exists on the GitHub side, but
has not yet been configured for git-mirror at all.
To give the script access to your repositories, you need to create an access
token for it. Go to "Personal Access Tokens" in your GitHub configuration, and
create a new token with the permissions admin:repo_hook and public_repo.
Add the token and the webhook URL to the top part of git-mirror.conf (right
below mail-sender):
github-token = pastethetokenhere
webhook-url = https://example.com/git-mirror/webhook.py
Now you can call the automatic setup script as follows:
./github-add-hooks.py -o UserName -e [email protected] \
-l ~/repositories/repo-name.git/ -n github-repo-name
Notice that the username is case-sensitive! This will do all the setup
on the GitHub side, and it will add an appropriate configuration block
to your local git-mirror.conf. You still have to manually add the
local git hook to gitolite. Once you are done, any push happening to
either gitolite or GitHub will be visible on the other side
immediately. This applies even to pull requests that you merge in the
GitHub web interface.
The script will only sync branches when they get pushed to. To initialize the
GitHub repository with all the branches that already exist, you can do git push --all [email protected]:user/repo.
You can find the sources in the git
repository (also available
on GitHub). Guess what, the
two are synced with this tool ;-) . They are provided under a
2-clause BSD
license. See the file
LICENSE-BSD for more details.
If you found a bug, or want to leave a comment, please send me a mail. I'm also happy about pull requests :)