git-mergetool: move show_tool_help to mergetool--lib

This is the first step in unifying "git difftool --tool-help" and
"git mergetool --tool-help".

Signed-off-by: John Keeping <john@keeping.me.uk>
Signed-off-by: David Aguilar <davvid@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

git-mergetool--lib.sh

@@ -174,6 +174,43 @@ list_merge_tool_candidates () {
 	esac
 }
 
+show_tool_help () {
+	TOOL_MODE=merge
+	list_merge_tool_candidates
+	unavailable= available= LF='
+'
+	for i in $tools
+	do
+		merge_tool_path=$(translate_merge_tool_path "$i")
+		if type "$merge_tool_path" >/dev/null 2>&1
+		then
+			available="$available$i$LF"
+		else
+			unavailable="$unavailable$i$LF"
+		fi
+	done
+	if test -n "$available"
+	then
+		echo "'git mergetool --tool=<tool>' may be set to one of the following:"
+		echo "$available" | sort | sed -e 's/^/	/'
+	else
+		echo "No suitable tool for 'git mergetool --tool=<tool>' found."
+	fi
+	if test -n "$unavailable"
+	then
+		echo
+		echo 'The following tools are valid, but not currently available:'
+		echo "$unavailable" | sort | sed -e 's/^/	/'
+	fi
+	if test -n "$unavailable$available"
+	then
+		echo
+		echo "Some of the tools listed above only work in a windowed"
+		echo "environment. If run in a terminal-only session, they will fail."
+	fi
+	exit 0
+}
+
 guess_merge_tool () {
 	list_merge_tool_candidates
 	echo >&2 "merge tool candidates: $tools"

git-mergetool.sh

@@ -315,43 +315,6 @@ merge_file () {
 	return 0
 }
 
-show_tool_help () {
-	TOOL_MODE=merge
-	list_merge_tool_candidates
-	unavailable= available= LF='
-'
-	for i in $tools
-	do
-		merge_tool_path=$(translate_merge_tool_path "$i")
-		if type "$merge_tool_path" >/dev/null 2>&1
-		then
-			available="$available$i$LF"
-		else
-			unavailable="$unavailable$i$LF"
-		fi
-	done
-	if test -n "$available"
-	then
-		echo "'git mergetool --tool=<tool>' may be set to one of the following:"
-		echo "$available" | sort | sed -e 's/^/	/'
-	else
-		echo "No suitable tool for 'git mergetool --tool=<tool>' found."
-	fi
-	if test -n "$unavailable"
-	then
-		echo
-		echo 'The following tools are valid, but not currently available:'
-		echo "$unavailable" | sort | sed -e 's/^/	/'
-	fi
-	if test -n "$unavailable$available"
-	then
-		echo
-		echo "Some of the tools listed above only work in a windowed"
-		echo "environment. If run in a terminal-only session, they will fail."
-	fi
-	exit 0
-}
-
 prompt=$(git config --bool mergetool.prompt || echo true)
 
 while test $# != 0