Add colour support in rebase and merge tree diff stats output.

The rebase and merge commands used diff-tree to display the summary stats of
what files had changed from the operation. diff-tree does not read the
diff ui configuration options, so the diff.color setting was not used.

Have rebase and merge call diff rather than diff-tree, which does read the
diff ui options.

Signed-off-by: James Bowes <jbowes@dangerouslyinc.com>
Signed-off-by: Junio C Hamano <junkio@cox.net>

git-merge.sh

@@ -90,7 +90,8 @@ finish () {
 	?*)
 		case "$no_summary" in
 		'')
-			git-diff-tree --stat --summary -M "$head" "$1"
+			# We want color (if set), but no pager
+			GIT_PAGER='' git-diff --stat --summary -M "$head" "$1"
 			;;
 		esac
 		;;

git-rebase.sh

@@ -307,7 +307,8 @@ fi
 if test -n "$verbose"
 then
 	echo "Changes from $mb to $onto:"
-	git-diff-tree --stat --summary "$mb" "$onto"
+	# We want color (if set), but no pager
+	GIT_PAGER='' git-diff --stat --summary "$mb" "$onto"
 fi
 
 # Rewind the head to "$onto"; this saves our current head in ORIG_HEAD.