packed_git: convert pack_local flag into a bitfield and add pack_keep

pack_keep will be set when a pack file has an associated .keep file.

Signed-off-by: Brandon Casey <casey@nrlssc.navy.mil>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

cache.h

@@ -671,7 +671,8 @@ extern struct packed_git {
 	int index_version;
 	time_t mtime;
 	int pack_fd;
-	int pack_local;
+	unsigned pack_local:1,
+		 pack_keep:1;
 	unsigned char sha1[20];
 	/* something like ".git/objects/pack/xxxxx.pack" */
 	char pack_name[FLEX_ARRAY]; /* more */

sha1_file.c

@@ -828,6 +828,11 @@ struct packed_git *add_packed_git(const char *path, int path_len, int local)
 		return NULL;
 	}
 	memcpy(p->pack_name, path, path_len);
+
+	strcpy(p->pack_name + path_len, ".keep");
+	if (!access(p->pack_name, F_OK))
+		p->pack_keep = 1;
+
 	strcpy(p->pack_name + path_len, ".pack");
 	if (stat(p->pack_name, &st) || !S_ISREG(st.st_mode)) {
 		free(p);