Merge branch 'lt/pathspec-negative'

The "negative" pathspec feature was somewhat more cumbersome to use
than necessary in that its short-hand used "!" which needed to be
escaped from shells, and it required "exclude from what?" specified.

* lt/pathspec-negative:
  pathspec: don't error out on all-exclusionary pathspec patterns
  pathspec magic: add '^' as alias for '!'

Documentation/glossary-content.txt

@@ -386,8 +386,10 @@ 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.  When there
+	is no non-exclude pathspec, the exclusion is applied to the
+	result set as if invoked without any pathspec.
 --
 
 [[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;
 
@@ -516,7 +522,7 @@ void parse_pathspec(struct pathspec *pathspec,
 	}
 
 	pathspec->nr = n;
-	ALLOC_ARRAY(pathspec->items, n);
+	ALLOC_ARRAY(pathspec->items, n + 1);
 	item = pathspec->items;
 	prefixlen = prefix ? strlen(prefix) : 0;
 
@@ -540,10 +546,15 @@ void parse_pathspec(struct pathspec *pathspec,
 		pathspec->magic |= item[i].magic;
 	}
 
-	if (nr_exclude == n)
-		die(_("There is nothing to exclude from by :(exclude) patterns.\n"
-		      "Perhaps you forgot to add either ':/' or '.' ?"));
-
+	/*
+	 * If everything is an exclude pattern, add one positive pattern
+	 * that matches everyting. We allocated an extra one for this.
+	 */
+	if (nr_exclude == n) {
+		int plen = (!(flags & PATHSPEC_PREFER_CWD)) ? 0 : prefixlen;
+		init_pathspec_item(item + n, 0, prefix, plen, "");
+		pathspec->nr++;
+	}
 
 	if (pathspec->magic & PATHSPEC_MAXDEPTH) {
 		if (flags & PATHSPEC_KEEP_ORDER)

t/t6132-pathspec-exclude.sh

@@ -25,8 +25,10 @@ EOF
 	test_cmp expect actual
 '
 
-test_expect_success 'exclude only should error out' '
-	test_must_fail git log --oneline --format=%s -- ":(exclude)sub"
+test_expect_success 'exclude only no longer errors out' '
+	git log --oneline --format=%s -- . ":(exclude)sub" >expect &&
+	git log --oneline --format=%s -- ":(exclude)sub" >actual &&
+	test_cmp expect actual
 '
 
 test_expect_success 't_e_i() exclude sub' '