Merge branch 'jk/interpret-branch-name' into maint

"git branch @" created refs/heads/@ as a branch, and in general the
code that handled @{-1} and @{upstream} was a bit too loose in
disambiguating.

* jk/interpret-branch-name:
  checkout: restrict @-expansions when finding branch
  strbuf_check_ref_format(): expand only local branches
  branch: restrict @-expansions when deleting
  t3204: test git-branch @-expansion corner cases
  interpret_branch_name: allow callers to restrict expansions
  strbuf_branchname: add docstring
  strbuf_branchname: drop return value
  interpret_branch_name: move docstring to header file
  interpret_branch_name(): handle auto-namelen for @{-1}

refs.c

@@ -404,7 +404,7 @@ int refname_match(const char *abbrev_name, const char *full_name)
 static char *substitute_branch_name(const char **string, int *len)
 {
 	struct strbuf buf = STRBUF_INIT;
-	int ret = interpret_branch_name(*string, *len, &buf);
+	int ret = interpret_branch_name(*string, *len, &buf, 0);
 
 	if (ret == *len) {
 		size_t size;