git-gui ignores core.hooksPath

Hi git devs,

First off, thanks for your awesome work!

I've been unhappy for quite a while that I had to configure the hooks manually for each of my repos - until I found out recently that there is the core.hooksPath config variable that (when set globally) allows me to specify a hooks directory to be used for all my repositories.

Now I was happy - for a few minutes, until I tested this feature in git-gui, and realized that it doesn't work there.

This seems to be caused by "proc githook_read", which says "set pchook [gitdir hooks $hook_name]" instead of querying "git config core.hooksPath" first - cf https://github.com/git/git/blob/2cc2e70264e0fcba04f9ef791d144bbc8b501206/git-gui/git-gui.sh#L627

Would be great if this could get fixed...

Thanks, Philipp