Git: Don't call post-receive hook when deleting a branch

Question

We are using a post-receive hook in Git to deploy a PHP "app". The script (Bash) checks the branch name and do a rsync on the correct server based on a prefix in the branch name.

This work pretty well, except for one thing: it tries to do a deployment when we delete a branch.

I checked at many places, and I didn't find a way to find out from the script if the operation is a delete.

Is there a way to achieve this. The script is on a bare repository (managed by Gitolite), it is not on the developers workstation.

Answer 1

When git receives a push, the post-receive hook is invoked and passed data on stdin about each ref that was delivered, in rows of <old-sha> <new-sha> <ref-name>, like so:

e1f5c274e296f1c5148161f9d4e5eb43a6743e54 1eea3f51cf926c3710f8fa4a06f503041c4597f0 refs/heads/master

When a branch is deleted, the <new-sha> entry is all zeros, like so:

6b239c481453c7fc2513b02e8aa0cd9c1ffa25cb 0000000000000000000000000000000000000000 refs/heads/foo

So, you can adjust your post-receive hook to detect this (and prevent this branch from triggering a deployment) using logic like:

#!/bin/sh -

while read OLDSHA NEWSHA REF ; do
  if [ "$NEWSHA" = "0000000000000000000000000000000000000000" ]; then
    # This ref has been deleted! Respond appropriately.
  fi
done

Remember that a single push can contain update multiple branches, too! You'll probably want to accumulate a set of branches that should be deployed, that begin with the appropriate prefix and have a nonzero NEWSHA.