ident: say whose identity is missing when giving user.name hint

If `user.name` and `user.email` have not been configured and the
user invokes:

    git commit --author=...

without specifying the committer identity, then Git errors out with
a message asking the user to configure `user.name` and `user.email`
but doesn't tell the user which attribution was missing. This can be
confusing for a user new to Git who isn't aware of the distinction
between user, author, and committer.

Give such users a bit more help by extending the error message to
also say which attribution is expected.

Signed-off-by: Junio C Hamano <gitster@pobox.com>

ident.c

@@ -345,18 +345,32 @@ person_only:
 	return 0;
 }
 
-static const char *env_hint =
-N_("\n"
-   "*** Please tell me who you are.\n"
-   "\n"
-   "Run\n"
-   "\n"
-   "  git config --global user.email \"you@example.com\"\n"
-   "  git config --global user.name \"Your Name\"\n"
-   "\n"
-   "to set your account\'s default identity.\n"
-   "Omit --global to set the identity only in this repository.\n"
-   "\n");
+
+static void ident_env_hint(enum want_ident whose_ident)
+{
+	switch (whose_ident) {
+	case WANT_AUTHOR_IDENT:
+		fputs(_("Author identity unknown\n"), stderr);
+		break;
+	case WANT_COMMITTER_IDENT:
+		fputs(_("Committer identity unknown\n"), stderr);
+		break;
+	default:
+		break;
+	}
+
+	fputs(_("\n"
+		"*** Please tell me who you are.\n"
+		"\n"
+		"Run\n"
+		"\n"
+		"  git config --global user.email \"you@example.com\"\n"
+		"  git config --global user.name \"Your Name\"\n"
+		"\n"
+		"to set your account\'s default identity.\n"
+		"Omit --global to set the identity only in this repository.\n"
+		"\n"), stderr);
+}
 
 const char *fmt_ident(const char *name, const char *email,
 		      enum want_ident whose_ident, const char *date_str, int flag)
@@ -375,12 +389,12 @@ const char *fmt_ident(const char *name, const char *email,
 	if (!email) {
 		if (strict && ident_use_config_only
 		    && !(ident_config_given & IDENT_MAIL_GIVEN)) {
-			fputs(_(env_hint), stderr);
+			ident_env_hint(whose_ident);
 			die(_("no email was given and auto-detection is disabled"));
 		}
 		email = ident_default_email();
 		if (strict && default_email_is_bogus) {
-			fputs(_(env_hint), stderr);
+			ident_env_hint(whose_ident);
 			die(_("unable to auto-detect email address (got '%s')"), email);
 		}
 	}
@@ -397,13 +411,13 @@ const char *fmt_ident(const char *name, const char *email,
 		if (!name) {
 			if (strict && ident_use_config_only
 			    && !(ident_config_given & IDENT_NAME_GIVEN)) {
-				fputs(_(env_hint), stderr);
+				ident_env_hint(whose_ident);
 				die(_("no name was given and auto-detection is disabled"));
 			}
 			name = ident_default_name();
 			using_default = 1;
 			if (strict && default_name_is_bogus) {
-				fputs(_(env_hint), stderr);
+				ident_env_hint(whose_ident);
 				die(_("unable to auto-detect name (got '%s')"), name);
 			}
 		}
@@ -411,7 +425,7 @@ const char *fmt_ident(const char *name, const char *email,
 			struct passwd *pw;
 			if (strict) {
 				if (using_default)
-					fputs(_(env_hint), stderr);
+					ident_env_hint(whose_ident);
 				die(_("empty ident name (for <%s>) not allowed"), email);
 			}
 			pw = xgetpwuid_self(NULL);

t/t7518-ident-corner-cases.sh

@@ -29,7 +29,18 @@ test_expect_success 'empty configured name does not auto-detect' '
 		sane_unset GIT_AUTHOR_NAME &&
 		test_must_fail \
 			git -c user.name= commit --allow-empty -m foo 2>err &&
-		test_i18ngrep "empty ident name" err
+		test_i18ngrep "empty ident name" err &&
+		test_i18ngrep "Author identity unknown" err
+	)
+'
+
+test_expect_success 'empty configured name does not auto-detect for committer' '
+	(
+		sane_unset GIT_COMMITTER_NAME &&
+		test_must_fail \
+			git -c user.name= commit --allow-empty -m foo 2>err &&
+		test_i18ngrep "empty ident name" err &&
+		test_i18ngrep "Committer identity unknown" err
 	)
 '