git-archive: don't die when repository uses subprojects

Both archive-tar and archive-zip needed to be taught about subprojects.
The tar function died when trying to read the subproject commit object,
while the zip function reported "unsupported file mode".

This fixes both by representing the subproject as an empty directory.

Signed-off-by: Lars Hjemli <hjemli@gmail.com>
Signed-off-by: Junio C Hamano <junkio@cox.net>

archive-tar.c

@@ -166,7 +166,7 @@ static void write_entry(const unsigned char *sha1, struct strbuf *path,
 	} else {
 		if (verbose)
 			fprintf(stderr, "%.*s\n", path->len, path->buf);
-		if (S_ISDIR(mode)) {
+		if (S_ISDIR(mode) || S_ISDIRLNK(mode)) {
 			*header.typeflag = TYPEFLAG_DIR;
 			mode = (mode | 0777) & ~tar_umask;
 		} else if (S_ISLNK(mode)) {
@@ -278,7 +278,7 @@ static int write_tar_entry(const unsigned char *sha1,
 	memcpy(path.buf, base, baselen);
 	memcpy(path.buf + baselen, filename, filenamelen);
 	path.len = baselen + filenamelen;
-	if (S_ISDIR(mode)) {
+	if (S_ISDIR(mode) || S_ISDIRLNK(mode)) {
 		strbuf_append_string(&path, "/");
 		buffer = NULL;
 		size = 0;

archive-zip.c

@@ -182,10 +182,10 @@ static int write_zip_entry(const unsigned char *sha1,
 		goto out;
 	}
 
-	if (S_ISDIR(mode)) {
+	if (S_ISDIR(mode) || S_ISDIRLNK(mode)) {
 		method = 0;
 		attr2 = 16;
-		result = READ_TREE_RECURSIVE;
+		result = (S_ISDIR(mode) ? READ_TREE_RECURSIVE : 0);
 		out = NULL;
 		uncompressed_size = 0;
 		compressed_size = 0;