pathspec magic: add '^' as alias for '!'

The choice of '!' for a negative pathspec ends up not only not matching
what we do for revisions, it's also a horrible character for shell
expansion since it needs quoting.

So add '^' as an alternative alias for an excluding pathspec entry.

Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Documentation/glossary-content.txt

@@ -386,8 +386,8 @@ Glob magic is incompatible with literal magic.
 
 exclude;;
 	After a path matches any non-exclude pathspec, it will be run
-	through all exclude pathspec (magic signature: `!`). If it
-	matches, the path is ignored.
+	through all exclude pathspec (magic signature: `!` or its
+	synonym `^`). If it matches, the path is ignored.
 --
 
 [[def_parent]]parent::

pathspec.c

@@ -224,6 +224,12 @@ static const char *parse_short_magic(unsigned *magic, const char *elem)
 		char ch = *pos;
 		int i;
 
+		/* Special case alias for '!' */
+		if (ch == '^') {
+			*magic |= PATHSPEC_EXCLUDE;
+			continue;
+		}
+
 		if (!is_pathspec_magic(ch))
 			break;