Subject: Re: [PATCH 7/7] mergetool--lib: Improve show_tool_help() output

From: John Keeping <[email-masked]>
Date: Fri, 25 Jan 2013 20:46:19 +0000

On Fri, Jan 25, 2013 at 12:16:42PM -0800, Junio C Hamano wrote:
> John Keeping <[email-masked]> writes:
> 
> > Actually, can we just change all of the above part of the loop to:
> >
> > 	test "$tool" = defaults && continue
> >
> > 	merge_tool_path=$(
> > 		setup_tool "$tool" >/dev/null 2>&1 &&
> > 		translate_merge_tool_path "$tool"
> > 	) || continue
> 
> Meaning "setup_tool ought to know which mode we are in and should
> fail if we are in merge mode and it does not support merging"?  That
> line of reasoning makes tons of sense to me, compared to this script
> implementing that logic for these scriptlets.

Yes, that's part of what setup_tool does.  It actually calls "exit" if
the "mode? && can_mode" test fails, which is why we need to call it in
the subshell.

I think this would get even better if we add a preparatory patch like
this, so we can just call setup_tool and then set merge_tool_path:

-- >8 --

diff --git a/git-mergetool--lib.sh b/git-mergetool--lib.sh
index 888ae3e..4644cbf 100644
--- a/git-mergetool--lib.sh
+++ b/git-mergetool--lib.sh
@@ -67,11 +67,11 @@ setup_tool () {
 	if merge_mode && ! can_merge
 	then
 		echo "error: '$tool' can not be used to resolve merges" >&2
-		exit 1
+		return 1
 	elif diff_mode && ! can_diff
 	then
 		echo "error: '$tool' can only be used to resolve merges" >&2
-		exit 1
+		return 1
 	fi
 	return 0
 }
@@ -100,7 +100,7 @@ run_merge_tool () {
 	status=0
 
 	# Bring tool-specific functions into scope
-	setup_tool "$1"
+	setup_tool "$1" || return
 
 	if merge_mode
 	then

-- 8< --
 
> How/when does translate_merge_tool_path fail?

It doesn't - the "|| continue" is to catch errors from setup_tool.

John