Git-hooks pre-push script does not receive input via STDIN

Question

The git-hooks pre-push documentation states that the first line of stdin will be populated with the local ref and sha, and the remote ref and sha as such:

<local ref> SP <local sha1> SP <remote ref> SP <remote sha1> LF

However, my simple pre-push script:

#!/bin/bash

echo "params=[$@]"

read line
echo "stdin=[$line]"

exit 1

returns the following output when a $git push is run:

params=[origin [url]:[branch].git]
stdin=[]
error: failed to push some refs to '[remote]'

The parameters to the script are as specified in the documentation (name and path of the remote). The error is expected because my script exits with a status of 1. However, I can't seem to figure out why I'm not receiving the local and remote refs on stdin as specified by the documentation.

Is this a bug in git? Or, am I missing something?

Answer 1

Apologies if this is stating the obvious, but if there's nothing to push, you won't get any lines on stdin. The sample .git/hooks/pre-push.sample has a while loop:

IFS=' '
while read local_ref local_sha remote_ref remote_sha
do
    ...
done

and that appears to work when I try it here with an echo inside that loop and nothing else - I get nothing when I have nothing to push, and output when I do.