config: "git config baa" should exit with status 1

We instead failed with an undocumented exit status 255.
Also define a "catch-all" status and document it.

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

Documentation/git-config.txt

@@ -54,16 +54,16 @@ configuration file by default, and options '--system', '--global',
 '--file <filename>' can be used to tell the command to write to
 that location (you can say '--local' but that is the default).
 
-This command will fail (with exit code ret) if:
+This command will fail with non-zero status upon error.  Some exit
+codes are:
 
 . The config file is invalid (ret=3),
 . can not write to the config file (ret=4),
 . no section or name was provided (ret=2),
 . the section or key is invalid (ret=1),
 . you try to unset an option which does not exist (ret=5),
-. you try to unset/set an option for which multiple lines match (ret=5),
-. you try to use an invalid regexp (ret=6), or
-. you use '--global' option without $HOME being properly set (ret=128).
+. you try to unset/set an option for which multiple lines match (ret=5), or
+. you try to use an invalid regexp (ret=6).
 
 On success, the command returns the exit code 0.
 

builtin/config.c

@@ -160,7 +160,7 @@ static int show_config(const char *key_, const char *value_, void *cb)
 
 static int get_value(const char *key_, const char *regex_)
 {
-	int ret = -1;
+	int ret = CONFIG_GENERIC_ERROR;
 	char *global = NULL, *repo_config = NULL;
 	const char *system_wide = NULL, *local;
 	struct config_include_data inc = CONFIG_INCLUDE_INIT;
@@ -198,11 +198,14 @@ static int get_value(const char *key_, const char *regex_)
 		if (regcomp(key_regexp, key, REG_EXTENDED)) {
 			fprintf(stderr, "Invalid key pattern: %s\n", key_);
 			free(key);
+			ret = CONFIG_INVALID_PATTERN;
 			goto free_strings;
 		}
 	} else {
-		if (git_config_parse_key(key_, &key, NULL))
+		if (git_config_parse_key(key_, &key, NULL)) {
+			ret = CONFIG_INVALID_KEY;
 			goto free_strings;
+		}
 	}
 
 	if (regex_) {
@@ -214,6 +217,7 @@ static int get_value(const char *key_, const char *regex_)
 		regexp = (regex_t*)xmalloc(sizeof(regex_t));
 		if (regcomp(regexp, regex_, REG_EXTENDED)) {
 			fprintf(stderr, "Invalid pattern: %s\n", regex_);
+			ret = CONFIG_INVALID_PATTERN;
 			goto free_strings;
 		}
 	}

cache.h

@@ -1141,6 +1141,7 @@ extern int update_server_info(int);
 #define CONFIG_NO_WRITE 4
 #define CONFIG_NOTHING_SET 5
 #define CONFIG_INVALID_PATTERN 6
+#define CONFIG_GENERIC_ERROR 7
 
 typedef int (*config_fn_t)(const char *, const char *, void *);
 extern int git_default_config(const char *, const char *, void *);