type_from_string_gently: make sure length matches

When commit fe8e3b7 refactored type_from_string to allow
input that was not NUL-terminated, it switched to using
strncmp instead of strcmp. But this means we check only the
first "len" bytes of the strings, and ignore any remaining
bytes in the object_type_string. We should make sure that it
is also "len" bytes, or else we would accept "comm" as
"commit", and so forth.

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

object.c

@@ -41,7 +41,8 @@ int type_from_string_gently(const char *str, ssize_t len, int gentle)
 		len = strlen(str);
 
 	for (i = 1; i < ARRAY_SIZE(object_type_strings); i++)
-		if (!strncmp(str, object_type_strings[i], len))
+		if (!strncmp(str, object_type_strings[i], len) &&
+		    object_type_strings[i][len] == '\0')
 			return i;
 
 	if (gentle)

t/t1007-hash-object.sh

@@ -201,4 +201,12 @@ test_expect_success 'corrupt tag' '
 	test_must_fail git hash-object -t tag --stdin </dev/null
 '
 
+test_expect_success 'hash-object complains about bogus type name' '
+	test_must_fail git hash-object -t bogus --stdin </dev/null
+'
+
+test_expect_success 'hash-object complains about truncated type name' '
+	test_must_fail git hash-object -t bl --stdin </dev/null
+'
+
 test_done