Re: git gui replaces amend message when prepare-commit-msg hook is used

> On Thu, Jul 4, 2013 at 1:34 PM, John Keeping <john@keeping.me.uk> wrote:
> > On Thu, Jul 04, 2013 at 12:47:28PM +0300, Orgad Shaneh wrote:
> >> Hi,
> >>
> >> If a prepare-commit-msg hook is used, git gui executes it for "New Commit".
> >>
> >> If the "New Commit" is selected, and then immediately "Amend" (before
> >> the hook returns), when the hook returns the message is replaced with
> >> the one produced by the hook.
> >
> > I think this is a problem with the hook you are running.  The hook is
> > given arguments specifying the message file and optionally the source of
> > whatever is already in the file (see githooks(5) for details).
> >
> > It sounds like your hook is blindly overwriting the file, rather than
> > preserving its contents in the cases where you wish to do so.
> 
> Let me try to explain.
> 
> When git gui is executed, it calls the prepare-commit-msg script with
> .git/PREPARE_COMMIT_MSG as an argument.
> 
> When amend is selected, the hook is *not* called at all (what would it
> prepare? The message is already committed)
> 
> Use the following hook to reproduce:
> --- snip ---
> #!/bin/sh
> 
> sleep 5
> echo "$@" >> /tmp/hook.log
> echo 'Hello hook' > "$1"
> --- snip ---
> 
> Now run git gui (or press F5 if it is already running), and before 5
> seconds pass, click Amend last commit. You'll see the commit's
> message, but when the 5 seconds pass it is replaced with "Hello hook".
> That's the bug.