From: Jeff King <peff@peff.net>
Date: Wed, 03 Feb 2010 09:31:51 GMT
Subject: Re: [BUG] - "git commit --amend" commits, when exiting the editor with no changes written
Message-ID: <20100203093150.GA23956@coredump.intra.peff.net>
In-Reply-To: <20100203061535.GA6566@cthulhu>

On Wed, Feb 03, 2010 at 01:15:35AM -0500, Larry D'Anna wrote:

> * Avery Pennarun (apenwarr@gmail.com) [100202 18:41]:
> > You can however add *new* stuff.  That's why I suggested adding an
> > option.  You could even make it a config option so you only have to
> > set it once (just like setting your preferred editor).
> 
> Or, he can set his $EDITOR to a script that checks the mtime.

Agreed. It could even look like this:

-- >8 --
$ cat >vi-must-edit <<'EOF'
#!/usr/bin/perl
sub mtime { (stat $_[0])[9] }
my $old = mtime($ARGV[-1]);
system('vi', @ARGV) and die "vi failed";
if (mtime($ARGV[-1]) == $old) {
  print STDERR "Aborting unmodified message\n";
  exit 1;
}
exit 0
EOF
$ chmod +x vi-must-edit
$ GIT_EDITOR=$PWD/vi-must-edit; export GIT_EDITOR
$ git commit --amend ;# and then quit the editor immediately
Aborting unmodified message
error: There was a problem with the editor 'vi-must-edit'.
Please supply the message using either -m or -F option.

-- 8< --

Do note, though, that there is a subtle race condition in using the
mtime. If you make a change and save within a second of the editor
starting, it will be ignored. To be thorough, you would probably want to
check the size and inode, as well.

-Peff