Suggest use of "git add file1 file2" when there is nothing to commit.

If a user modifies files and runs 'git commit' (without the very
useful -a option) and they have not yet updated the index they
are probably coming from another SCM-like tool which would perform
the same as 'git commit -a' in this case.  Showing the user their
current status and a final line of "nothing to commit" is not very
reassuring, as the user might believe that Git did not recognize
their files were modified.

Instead we can suggest as part of the 'nothing to commit' message
that the user invoke 'git add' to add files to their next commit.

Suggested by Andy Parkins' Git 'niggles' list
(<200612132237.10051.andyparkins@gmail.com>).

Signed-off-by: Shawn O. Pearce <spearce@spearce.org>
Signed-off-by: Junio C Hamano <junkio@cox.net>

git-commit.sh

@@ -520,7 +520,7 @@ then
 	current="$(git-rev-parse --verify HEAD)"
 else
 	if [ -z "$(git-ls-files)" ]; then
-		echo >&2 Nothing to commit
+		echo >&2 'nothing to commit (use "git add file1 file2" to include for commit)'
 		exit 1
 	fi
 	PARENTS=""

wt-status.c

@@ -15,6 +15,7 @@ static char wt_status_colors[][COLOR_MAXLEN] = {
 	"\033[31m", /* WT_STATUS_CHANGED: red */
 	"\033[31m", /* WT_STATUS_UNTRACKED: red */
 };
+static const char* use_add_msg = "use \"git add file1 file2\" to include for commit";
 
 static int parse_status_slot(const char *var, int offset)
 {
@@ -162,8 +163,7 @@ static void wt_status_print_changed_cb(struct diff_queue_struct *q,
 {
 	int i;
 	if (q->nr)
-		wt_status_print_header("Changed but not updated",
-				"use git-add on files to include for commit");
+		wt_status_print_header("Changed but not updated", use_add_msg);
 	for (i = 0; i < q->nr; i++)
 		wt_status_print_filepair(WT_STATUS_CHANGED, q->queue[i]);
 	if (q->nr)
@@ -249,8 +249,7 @@ static void wt_status_print_untracked(const struct wt_status *s)
 				continue;
 		}
 		if (!shown_header) {
-			wt_status_print_header("Untracked files",
-				"use \"git add\" to add to commit");
+			wt_status_print_header("Untracked files", use_add_msg);
 			shown_header = 1;
 		}
 		color_printf(color(WT_STATUS_HEADER), "#\t");
@@ -292,7 +291,9 @@ void wt_status_print(struct wt_status *s)
 	if (s->verbose && !s->is_initial)
 		wt_status_print_verbose(s);
 	if (!s->commitable)
-		printf("%s\n", s->amend ? "# No changes" : "nothing to commit");
+		printf("%s (%s)\n",
+			s->amend ? "# No changes" : "nothing to commit",
+			use_add_msg);
 }
 
 int git_status_config(const char *k, const char *v)