index-pack: Track the object_entry that creates each base_data

If we free the data stored within a base_data we need the struct
object_entry to get the data back again for use with another dependent
delta.  Storing the object_entry* in base_data makes it simple to call
get_data_from_pack() to recover the compressed information.

This however means that we must add the missing base object to the end of
our packfile prior to calling resolve_delta() on each of the dependent
deltas.  Adding the base first ensures we can read the base back from the
pack we are indexing, as if it had been included by the remote side.

Signed-off-by: Shawn O. Pearce <spearce@spearce.org>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

index-pack.c

@@ -29,6 +29,7 @@ union delta_base {
 struct base_data {
 	struct base_data *base;
 	struct base_data *child;
+	struct object_entry *obj;
 	void *data;
 	unsigned long size;
 };
@@ -475,6 +476,7 @@ static void resolve_delta(struct object_entry *delta_obj,
 	sha1_object(result.data, result.size, type, delta_obj->idx.sha1);
 	nr_resolved_deltas++;
 
+	result.obj = delta_obj;
 	link_base_data(base_obj, &result);
 
 	hashcpy(delta_base.sha1, delta_obj->idx.sha1);
@@ -587,6 +589,7 @@ static void parse_pack_objects(unsigned char *sha1)
 			continue;
 		base_obj.data = get_data_from_pack(obj);
 		base_obj.size = obj->size;
+		base_obj.obj = obj;
 		link_base_data(NULL, &base_obj);
 
 		if (ref)
@@ -632,7 +635,8 @@ static int write_compressed(int fd, void *in, unsigned int size, uint32_t *obj_c
 	return size;
 }
 
-static void append_obj_to_pack(const unsigned char *sha1, void *buf,
+static struct object_entry *append_obj_to_pack(
+			       const unsigned char *sha1, void *buf,
 			       unsigned long size, enum object_type type)
 {
 	struct object_entry *obj = &objects[nr_objects++];
@@ -653,6 +657,7 @@ static void append_obj_to_pack(const unsigned char *sha1, void *buf,
 	obj[1].idx.offset = obj[0].idx.offset + n;
 	obj[1].idx.offset += write_compressed(output_fd, buf, size, &obj[0].idx.crc32);
 	hashcpy(obj->idx.sha1, sha1);
+	return obj;
 }
 
 static int delta_pos_compare(const void *_a, const void *_b)
@@ -696,6 +701,12 @@ static void fix_unresolved_deltas(int nr_unresolved)
 		base_obj.data = read_sha1_file(d->base.sha1, &type, &base_obj.size);
 		if (!base_obj.data)
 			continue;
+
+		if (check_sha1_signature(d->base.sha1, base_obj.data,
+				base_obj.size, typename(type)))
+			die("local object %s is corrupt", sha1_to_hex(d->base.sha1));
+		base_obj.obj = append_obj_to_pack(d->base.sha1, base_obj.data,
+			base_obj.size, type);
 		link_base_data(NULL, &base_obj);
 
 		find_delta_children(&d->base, &first, &last);
@@ -705,11 +716,6 @@ static void fix_unresolved_deltas(int nr_unresolved)
 				resolve_delta(child, &base_obj, type);
 		}
 
-		if (check_sha1_signature(d->base.sha1, base_obj.data,
-				base_obj.size, typename(type)))
-			die("local object %s is corrupt", sha1_to_hex(d->base.sha1));
-		append_obj_to_pack(d->base.sha1, base_obj.data,
-			base_obj.size, type);
 		unlink_base_data(&base_obj);
 		display_progress(progress, nr_resolved_deltas);
 	}