Putting Git hooks into a repository

I generally agree with Scy, with a couple of additional suggestions, enough that it’s worth a separate answer.

First, you should write a script which creates the appropriate symlinks, especially if these hooks are about enforcing policy or creating useful notifications. People will be much more likely to use the hooks if they can just type bin/create-hook-symlinks than if they have to do it themselves.

Second, directly symlinking hooks prevents users from adding in their own personal hooks. For example, I rather like the sample pre-commit hook which makes sure I don’t have any white space errors. A great way around this is to drop in a hook wrapper script in your repository, and symlink all of the hooks to it.

The wrapper can then examine $0 (assuming it’s a Bash script; an equivalent like argv[0] otherwise) to figure out which hook it was invoked as, then invoke the appropriate hook within your repository, as well as the appropriate user’s hook, which will have to be renamed, passing all the arguments to each. Quick example:

#!/bin/bash
if [ -x $0.local ]; then
    $0.local "[email protected]" || exit $?
fi
if [ -x tracked_hooks/$(basename $0) ]; then
    tracked_hooks/$(basename $0) "[email protected]" || exit $?
fi

The installation script would move all pre-existing hooks to the side (append .local to their names), and symlink all known hook names to the above script:

#!/bin/bash
HOOK_NAMES="applypatch-msg pre-applypatch post-applypatch pre-commit prepare-commit-msg commit-msg post-commit pre-rebase post-checkout post-merge pre-receive update post-receive post-update pre-auto-gc"
# assuming the script is in a bin directory, one level into the repo
HOOK_DIR=$(git rev-parse --show-toplevel)/.git/hooks

for hook in $HOOK_NAMES; do
    # If the hook already exists, is executable, and is not a symlink
    if [ ! -h $HOOK_DIR/$hook -a -x $HOOK_DIR/$hook ]; then
        mv $HOOK_DIR/$hook $HOOK_DIR/$hook.local
    fi
    # create the symlink, overwriting the file if it exists
    # probably the only way this would happen is if you're using an old version of git
    # -- back when the sample hooks were not executable, instead of being named ____.sample
    ln -s -f ../../bin/hooks-wrapper $HOOK_DIR/$hook
done

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