Improve "nothing to commit" part of status output

Previously git-status in a clean working directory would advice the user to use
git add. This isn't very helpful when there is nothing to add in the working
directory, therefore note a clean working directory while displaying the other
sections and print the appropriate message for each case.

Signed-off-by: Jürgen Rühle <j-r@online.de>
Signed-off-by: Junio C Hamano <junkio@cox.net>

wt-status.c

@@ -51,6 +51,8 @@ void wt_status_prepare(struct wt_status *s)
 	s->verbose = 0;
 	s->commitable = 0;
 	s->untracked = 0;
+
+	s->workdir_clean = 1;
 }
 
 static void wt_status_print_header(const char *main, const char *sub)
@@ -162,9 +164,12 @@ static void wt_status_print_changed_cb(struct diff_queue_struct *q,
                         struct diff_options *options,
                         void *data)
 {
+	struct wt_status *s = data;
 	int i;
-	if (q->nr)
+	if (q->nr) {
+		s->workdir_clean = 0;
 		wt_status_print_header("Changed but not added", use_add_msg);
+	}
 	for (i = 0; i < q->nr; i++)
 		wt_status_print_filepair(WT_STATUS_CHANGED, q->queue[i]);
 	if (q->nr)
@@ -215,7 +220,7 @@ static void wt_status_print_changed(struct wt_status *s)
 	run_diff_files(&rev, 0);
 }
 
-static void wt_status_print_untracked(const struct wt_status *s)
+static void wt_status_print_untracked(struct wt_status *s)
 {
 	struct dir_struct dir;
 	const char *x;
@@ -250,6 +255,7 @@ static void wt_status_print_untracked(const struct wt_status *s)
 				continue;
 		}
 		if (!shown_header) {
+			s->workdir_clean = 0;
 			wt_status_print_header("Untracked files", use_add_msg);
 			shown_header = 1;
 		}
@@ -291,10 +297,16 @@ void wt_status_print(struct wt_status *s)
 
 	if (s->verbose && !s->is_initial)
 		wt_status_print_verbose(s);
-	if (!s->commitable)
-		printf("%s (%s)\n",
-			s->amend ? "# No changes" : "nothing to commit",
-			use_add_msg);
+	if (!s->commitable) {
+		if (s->amend)
+			printf("# No changes\n");
+		else if (s->workdir_clean)
+			printf(s->is_initial
+			       ? "nothing to commit\n"
+			       : "nothing to commit (working directory matches HEAD)\n");
+		else
+			printf("no changes added to commit (use \"git add\" and/or \"git commit [-a|-i|-o]\")\n");
+	}
 }
 
 int git_status_config(const char *k, const char *v)

wt-status.h

@@ -16,6 +16,7 @@ struct wt_status {
 	int verbose;
 	int amend;
 	int untracked;
+	int workdir_clean;
 };
 
 int git_status_config(const char *var, const char *value);