Do not allow ".lock" at the end of any refname component

Allowing any refname component to end with ".lock" is looking for
trouble; for example,

    $ git br foo.lock/bar
    $ git br foo
    fatal: Unable to create '[...]/.git/refs/heads/foo.lock': File exists.

Therefore, do not allow any refname component to end with ".lock".

Signed-off-by: Michael Haggerty <mhagger@alum.mit.edu>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Documentation/git-check-ref-format.txt

@@ -28,7 +28,7 @@ git imposes the following rules on how references are named:
 
 . They can include slash `/` for hierarchical (directory)
   grouping, but no slash-separated component can begin with a
-  dot `.`.
+  dot `.` or end with the sequence `.lock`.
 
 . They must contain at least one `/`. This enforces the presence of a
   category like `heads/`, `tags/` etc. but the actual names are not
@@ -47,8 +47,6 @@ git imposes the following rules on how references are named:
 
 . They cannot end with a slash `/` nor a dot `.`.
 
-. They cannot end with the sequence `.lock`.
-
 . They cannot contain a sequence `@{`.
 
 . They cannot contain a `\`.

refs.c

@@ -898,6 +898,8 @@ static int check_refname_component(const char *ref)
 		return -1; /* Component has zero length. */
 	if (ref[0] == '.')
 		return -1; /* Component starts with '.'. */
+	if (cp - ref >= 5 && !memcmp(cp - 5, ".lock", 5))
+		return -1; /* Refname ends with ".lock". */
 	return cp - ref;
 }
 
@@ -931,8 +933,6 @@ int check_refname_format(const char *ref, int flags)
 
 	if (ref[component_len - 1] == '.')
 		return -1; /* Refname ends with '.'. */
-	if (component_len >= 5 && !memcmp(&ref[component_len - 5], ".lock", 5))
-		return -1; /* Refname ends with ".lock". */
 	if (!(flags & REFNAME_ALLOW_ONELEVEL) && component_count < 2)
 		return -1; /* Refname has only one component. */
 	return 0;

t/t1402-check-ref-format.sh

@@ -43,8 +43,8 @@ invalid_ref 'heads/foo?bar'
 valid_ref 'foo./bar'
 invalid_ref 'heads/foo.lock'
 invalid_ref 'heads///foo.lock'
-valid_ref 'foo.lock/bar'
-valid_ref 'foo.lock///bar'
+invalid_ref 'foo.lock/bar'
+invalid_ref 'foo.lock///bar'
 valid_ref 'heads/foo@bar'
 invalid_ref 'heads/v@{ation'
 invalid_ref 'heads/foo\bar'
@@ -160,7 +160,7 @@ invalid_ref_normalized 'heads/./foo'
 invalid_ref_normalized 'heads\foo'
 invalid_ref_normalized 'heads/foo.lock'
 invalid_ref_normalized 'heads///foo.lock'
-valid_ref_normalized 'foo.lock/bar' 'foo.lock/bar'
-valid_ref_normalized 'foo.lock///bar' 'foo.lock/bar'
+invalid_ref_normalized 'foo.lock/bar'
+invalid_ref_normalized 'foo.lock///bar'
 
 test_done