Forbid pattern maching characters in refnames.

by marking '?', '*', and '[' as bad_ref_char().

Signed-off-by: Junio C Hamano <junkio@cox.net>

Documentation/git-check-ref-format.txt

@@ -26,13 +26,15 @@ imposes the following rules on how refs are named:
 
 . It cannot have ASCII control character (i.e. bytes whose
   values are lower than \040, or \177 `DEL`), space, tilde `~`,
-  caret `{caret}`, or colon `:` anywhere;
+  caret `{caret}`, colon `:`, question-mark `?`, asterisk `*`,
+  or open bracket `[` anywhere;
 
 . It cannot end with a slash `/`.
 
 These rules makes it easy for shell script based tools to parse
-refnames, and also avoids ambiguities in certain refname
-expressions (see gitlink:git-rev-parse[1]).  Namely:
+refnames, pathname expansion by the shell when a refname is used
+unquoted (by mistake), and also avoids ambiguities in certain
+refname expressions (see gitlink:git-rev-parse[1]).  Namely:
 
 . double-dot `..` are often used as in `ref1..ref2`, and in some
   context this notation means `{caret}ref1 ref2` (i.e. not in

refs.c

@@ -313,7 +313,9 @@ int write_ref_sha1(const char *ref, int fd, const unsigned char *sha1)
 static inline int bad_ref_char(int ch)
 {
 	return (((unsigned) ch) <= ' ' ||
-		ch == '~' || ch == '^' || ch == ':');
+		ch == '~' || ch == '^' || ch == ':' ||
+		/* 2.13 Pattern Matching Notation */
+		ch == '?' || ch == '*' || ch == '[');
 }
 
 int check_ref_format(const char *ref)