gitaly-hooks

README

gitaly-hooks

gitaly-hooks is a binary that is the single point of entry for git hooks through gitaly.

How is it invoked?

gitaly-hooks has the following subcommands:

subcommand	purpose	arguments	stdin
check	checks if the hooks can reach the gitlab server	none	none
pre-receive	used as the git pre-receive hook	none	<old-value> SP <new-value> SP <ref-name> LF
update	used as the git update hook	<ref-name> <old-object> <new-object>	none
post-receive	used as the git post-receive hook	none	<old-value> SP <new-value> SP <ref-name> LF
git	used as the git pack-objects hook	pack-objects [--stdout] [--shallow-file]	<object-list>

Where is it invoked from?

There are three main code paths that call gitaly-hooks.

git receive-pack (SSH & HTTP)

We have two RPCs that perform the git receive-pack function, SSHReceivePack and PostReceivePack.

Both of these RPCs, when executing git receive-pack, set core.hooksPath to the path of the gitaly-hooks binary. That happens here in ReceivePackConfig.

Operations service RPCs

In the operations service there are RPCs that call out to gitaly-ruby, which then do certain operations that execute git hooks. This is accomplished through the with_hooks method here. Eventually the hook.rb is called, which then calls the gitaly-hooks binary. This method doesn't rely on git to run the hooks. Instead, the arguments and input to the hooks are built in ruby and then get shelled out to gitaly-hooks.

git upload-pack (SSH & HTTP)

Only when the pack-objects cache is enabled in Gitaly's configuration file.

SSHUploadPack and PostUploadPack, when executing git upload-pack, set uploadpack.packObjectsHook to the path of the gitaly-hooks binary. Afterward, when git upload-pack requests packfile data, it calls gitaly-hooks binary instead of git pack-objects. That happens here in WithPackObjectsHookEnv

What does gitaly-hooks do?

gitaly-hooks will take the arguments and make an RPC call to PreReceiveHook, UpdateHook, PostReceiveHook, or PackObjectsHook accordingly.