add: use advise function to display hints

Use the advise function in advice.c to display hints to the users, as
it provides a neat and a standard format for hint messages, i.e: the
text is colored in yellow and the line starts by the word "hint:".

Also this will enable us to control the messages using advice.*
configuration variables.

Signed-off-by: Heba Waly <heba.waly@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

advice.c

@@ -31,6 +31,7 @@ int advice_graft_file_deprecated = 1;
 int advice_checkout_ambiguous_remote_branch_name = 1;
 int advice_nested_tag = 1;
 int advice_submodule_alternate_error_strategy_die = 1;
+int advice_add_nothing = 1;
 
 static int advice_use_color = -1;
 static char advice_colors[][COLOR_MAXLEN] = {
@@ -91,6 +92,7 @@ static struct {
 	{ "checkoutAmbiguousRemoteBranchName", &advice_checkout_ambiguous_remote_branch_name },
 	{ "nestedTag", &advice_nested_tag },
 	{ "submoduleAlternateErrorStrategyDie", &advice_submodule_alternate_error_strategy_die },
+	{ "addNothing", &advice_add_nothing },
 
 	/* make this an alias for backward compatibility */
 	{ "pushNonFastForward", &advice_push_update_rejected }

advice.h

@@ -31,6 +31,7 @@ extern int advice_graft_file_deprecated;
 extern int advice_checkout_ambiguous_remote_branch_name;
 extern int advice_nested_tag;
 extern int advice_submodule_alternate_error_strategy_die;
+extern int advice_add_nothing;
 
 int git_default_advice_config(const char *var, const char *value);
 __attribute__((format (printf, 1, 2)))

builtin/add.c

@@ -390,7 +390,8 @@ static int add_files(struct dir_struct *dir, int flags)
 		fprintf(stderr, _(ignore_error));
 		for (i = 0; i < dir->ignored_nr; i++)
 			fprintf(stderr, "%s\n", dir->ignored[i]->name);
-		fprintf(stderr, _("Use -f if you really want to add them.\n"));
+		if (advice_add_nothing)
+			advise(_("Use -f if you really want to add them.\n"));
 		exit_status = 1;
 	}
 
@@ -480,7 +481,8 @@ int cmd_add(int argc, const char **argv, const char *prefix)
 
 	if (require_pathspec && pathspec.nr == 0) {
 		fprintf(stderr, _("Nothing specified, nothing added.\n"));
-		fprintf(stderr, _("Maybe you wanted to say 'git add .'?\n"));
+		if (advice_add_nothing)
+			advise( _("Maybe you wanted to say 'git add .'?\n"));
 		return 0;
 	}
 

t/t3700-add.sh

@@ -326,7 +326,7 @@ test_expect_success 'git add --dry-run of an existing file output' "
 cat >expect.err <<\EOF
 The following paths are ignored by one of your .gitignore files:
 ignored-file
-Use -f if you really want to add them.
+hint: Use -f if you really want to add them.
 EOF
 cat >expect.out <<\EOF
 add 'track-this'