add: don't complain when adding empty project root

This behavior was added in 07d7bed (add: don't complain when adding
empty project root - 2009-04-28) then broken by 84b8b5d (remove
match_pathspec() in favor of match_pathspec_depth() -
2013-07-14). Reinstate it.

Noticed-by: Thomas Ferris Nicolaisen <tfnico@gmail.com>
Signed-off-by: Nguyễn Thái Ngọc Duy <pclouds@gmail.com>
Reviewed-by: Jonathan Nieder <jrnieder@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
diff --git a/builtin/add.c b/builtin/add.c
index 226f758..d7e3e44 100644
--- a/builtin/add.c
+++ b/builtin/add.c
@@ -544,7 +544,7 @@
 
 		for (i = 0; i < pathspec.nr; i++) {
 			const char *path = pathspec.items[i].match;
-			if (!seen[i] &&
+			if (!seen[i] && path[0] &&
 			    ((pathspec.items[i].magic &
 			      (PATHSPEC_GLOB | PATHSPEC_ICASE)) ||
 			     !file_exists(path))) {
diff --git a/t/t3700-add.sh b/t/t3700-add.sh
index aab86e8..fe274e2 100755
--- a/t/t3700-add.sh
+++ b/t/t3700-add.sh
@@ -272,6 +272,25 @@
 	! (git ls-files | grep "non-existent")
 '
 
+test_expect_success 'git add -A on empty repo does not error out' '
+	rm -fr empty &&
+	git init empty &&
+	(
+		cd empty &&
+		git add -A . &&
+		git add -A
+	)
+'
+
+test_expect_success '"git add ." in empty repo' '
+	rm -fr empty &&
+	git init empty &&
+	(
+		cd empty &&
+		git add .
+	)
+'
+
 test_expect_success 'git add --dry-run of existing changed file' "
 	echo new >>track-this &&
 	git add --dry-run track-this >actual 2>&1 &&