Catch empty pathnames in trees during fsck

Released versions of fast-import have been able to create a tree that
contains files or subtrees that contain no name.  Unfortunately these
trees aren't valid, but people may have actually tried to create them
due to bugs in import-tars.perl or their own fast-import frontend.

We now look for this unusual condition and warn the user if at
least one of their tree objects contains the problem.

Signed-off-by: Shawn O. Pearce <spearce@spearce.org>
Signed-off-by: Junio C Hamano <junkio@cox.net>

builtin-fsck.c

@@ -218,6 +218,7 @@ static int fsck_tree(struct tree *item)
 {
 	int retval;
 	int has_full_path = 0;
+	int has_empty_name = 0;
 	int has_zero_pad = 0;
 	int has_bad_modes = 0;
 	int has_dup_entries = 0;
@@ -241,6 +242,8 @@ static int fsck_tree(struct tree *item)
 
 		if (strchr(name, '/'))
 			has_full_path = 1;
+		if (!*name)
+			has_empty_name = 1;
 		has_zero_pad |= *(char *)desc.buffer == '0';
 		update_tree_entry(&desc);
 
@@ -289,6 +292,9 @@ static int fsck_tree(struct tree *item)
 	if (has_full_path) {
 		objwarning(&item->object, "contains full pathnames");
 	}
+	if (has_empty_name) {
+		objwarning(&item->object, "contains empty pathname");
+	}
 	if (has_zero_pad) {
 		objwarning(&item->object, "contains zero-padded file modes");
 	}