packed-ref cache: forbid dot-components in refnames

Since v1.7.9-rc1~10^2 (write_head_info(): handle "extra refs" locally,
2012-01-06), this trick to keep track of ".have" refs that are only
valid on the wire and not on the filesystem is not needed any more.

Simplify by removing support for the REFNAME_DOT_COMPONENT flag.

This means we'll be slightly stricter with invalid refs found in a
packed-refs file or during clone.  read_loose_refs() already checks
for and skips refnames with .components so it is not affected.

Signed-off-by: Jonathan Nieder <jrnieder@gmail.com>
Reviewed-by: Ronnie Sahlberg <sahlberg@google.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

refs.c

@@ -70,16 +70,8 @@ static int check_refname_component(const char *refname, int flags)
 out:
 	if (cp == refname)
 		return 0; /* Component has zero length. */
-	if (refname[0] == '.') {
-		if (!(flags & REFNAME_DOT_COMPONENT))
+	if (refname[0] == '.')
 		return -1; /* Component starts with '.'. */
-		/*
-		 * Even if leading dots are allowed, don't allow "."
-		 * as a component (".." is prevented by a rule above).
-		 */
-		if (refname[1] == '\0')
-			return -1; /* Component equals ".". */
-	}
 	if (cp - refname >= LOCK_SUFFIX_LEN &&
 	    !memcmp(cp - LOCK_SUFFIX_LEN, LOCK_SUFFIX, LOCK_SUFFIX_LEN))
 		return -1; /* Refname ends with ".lock". */
@@ -290,7 +282,7 @@ static struct ref_entry *create_ref_entry(const char *refname,
 	struct ref_entry *ref;
 
 	if (check_name &&
-	    check_refname_format(refname, REFNAME_ALLOW_ONELEVEL|REFNAME_DOT_COMPONENT))
+	    check_refname_format(refname, REFNAME_ALLOW_ONELEVEL))
 		die("Reference has invalid format: '%s'", refname);
 	len = strlen(refname) + 1;
 	ref = xmalloc(sizeof(struct ref_entry) + len);

refs.h

@@ -229,7 +229,6 @@ extern int for_each_reflog(each_ref_fn, void *);
 
 #define REFNAME_ALLOW_ONELEVEL 1
 #define REFNAME_REFSPEC_PATTERN 2
-#define REFNAME_DOT_COMPONENT 4
 
 /*
  * Return 0 iff refname has the correct format for a refname according
@@ -237,10 +236,7 @@ extern int for_each_reflog(each_ref_fn, void *);
  * If REFNAME_ALLOW_ONELEVEL is set in flags, then accept one-level
  * reference names.  If REFNAME_REFSPEC_PATTERN is set in flags, then
  * allow a "*" wildcard character in place of one of the name
- * components.  No leading or repeated slashes are accepted.  If
- * REFNAME_DOT_COMPONENT is set in flags, then allow refname
- * components to start with "." (but not a whole component equal to
- * "." or "..").
+ * components.  No leading or repeated slashes are accepted.
  */
 extern int check_refname_format(const char *refname, int flags);