Merge branch 'jc/pack-reuse'

* jc/pack-reuse:
  pack-objects: avoid delta chains that are too long.
  git-repack: allow passing a couple of flags to pack-objects.
  pack-objects: finishing touches.
  pack-objects: reuse data from existing packs.

diff --combined sha1_file.c
index 1d799f7,0a3a721..9cab99a
--- 1/sha1_file.c
--- 2/sha1_file.c
+++ b/sha1_file.c
@@@ -551,10 -551,8 +551,10 @@@ static void prepare_packed_git_one(cha
        sprintf(path, "%s/pack", objdir);
        len = strlen(path);
        dir = opendir(path);
 -      if (!dir)
 +      if (!dir) {
 +              fprintf(stderr, "unable to open object pack directory: %s: %s\n", path, strerror(errno));
                return;
 +      }
        path[len++] = '/';
        while ((de = readdir(dir)) != NULL) {
                int namelen = strlen(de->d_name);
@@@ -828,6 -826,25 +828,25 @@@ static unsigned long unpack_object_head
        return offset;
  }
  
+ int check_reuse_pack_delta(struct packed_git *p, unsigned long offset,
+                          unsigned char *base, unsigned long *sizep,
+                          enum object_type *kindp)
+ {
+       unsigned long ptr;
+       int status = -1;
+ 
+       use_packed_git(p);
+       ptr = offset;
+       ptr = unpack_object_header(p, ptr, kindp, sizep);
+       if (*kindp != OBJ_DELTA)
+               goto done;
+       memcpy(base, p->pack_base + ptr, 20);
+       status = 0;
+  done:
+       unuse_packed_git(p);
+       return status;
+ }
+ 
  void packed_object_info_detail(struct pack_entry *e,
                               char *type,
                               unsigned long *size,