parse-options: abbreviation engine fix.

When an option could be an ambiguous abbreviation of two options, the code
used to error out.  Even if an exact match would have occured later.

Test and original patch by Pierre Habouzit.

Signed-off-by: Johannes Schindelin <Johannes.Schindelin@gmx.de>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

parse-options.c

@@ -119,8 +119,8 @@ static int parse_long_opt(struct optparse_t *p, const char *arg,
                           const struct option *options)
 {
 	const char *arg_end = strchr(arg, '=');
-	const struct option *abbrev_option = NULL;
-	int abbrev_flags = 0;
+	const struct option *abbrev_option = NULL, *ambiguous_option = NULL;
+	int abbrev_flags = 0, ambiguous_flags = 0;
 
 	if (!arg_end)
 		arg_end = arg + strlen(arg);
@@ -137,16 +137,16 @@ static int parse_long_opt(struct optparse_t *p, const char *arg,
 			/* abbreviated? */
 			if (!strncmp(options->long_name, arg, arg_end - arg)) {
 is_abbreviated:
-				if (abbrev_option)
-					return error("Ambiguous option: %s "
-						"(could be --%s%s or --%s%s)",
-						arg,
-						(flags & OPT_UNSET) ?
-							"no-" : "",
-						options->long_name,
-						(abbrev_flags & OPT_UNSET) ?
-							"no-" : "",
-						abbrev_option->long_name);
+				if (abbrev_option) {
+					/*
+					 * If this is abbreviated, it is
+					 * ambiguous. So when there is no
+					 * exact match later, we need to
+					 * error out.
+					 */
+					ambiguous_option = abbrev_option;
+					ambiguous_flags = abbrev_flags;
+				}
 				if (!(flags & OPT_UNSET) && *arg_end)
 					p->opt = arg_end + 1;
 				abbrev_option = options;
@@ -176,6 +176,15 @@ static int parse_long_opt(struct optparse_t *p, const char *arg,
 		}
 		return get_value(p, options, flags);
 	}
+
+	if (ambiguous_option)
+		return error("Ambiguous option: %s "
+			"(could be --%s%s or --%s%s)",
+			arg,
+			(ambiguous_flags & OPT_UNSET) ?  "no-" : "",
+			ambiguous_option->long_name,
+			(abbrev_flags & OPT_UNSET) ?  "no-" : "",
+			abbrev_option->long_name);
 	if (abbrev_option)
 		return get_value(p, abbrev_option, abbrev_flags);
 	return error("unknown option `%s'", arg);

t/t0040-parse-options.sh

@@ -18,6 +18,7 @@ string options
     -s, --string <string>
                           get a string
     --string2 <str>       get another string
+    --st <st>             get another string (pervert ordering)
 
 EOF
 
@@ -90,4 +91,16 @@ test_expect_failure 'ambiguously abbreviated option' '
         test $? != 129
 '
 
+cat > expect << EOF
+boolean: 0
+integer: 0
+string: 123
+EOF
+
+test_expect_success 'non ambiguous option (after two options it abbreviates)' '
+	test-parse-options --st 123 > output 2> output.err &&
+	test ! -s output.err &&
+	git diff expect output
+'
+
 test_done

test-parse-options.c

@@ -18,6 +18,7 @@ int main(int argc, const char **argv)
 		OPT_GROUP("string options"),
 		OPT_STRING('s', "string", &string, "string", "get a string"),
 		OPT_STRING(0, "string2", &string, "str", "get another string"),
+		OPT_STRING(0, "st", &string, "st", "get another string (pervert ordering)"),
 		OPT_END(),
 	};
 	int i;