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make git-pack-objects able to create deltas with offset to base
This is enabled with --delta-base-offset only, and doesn't work with pack data reuse yet. The idea is to allow for the fetch protocol to use an extension flag to notify the remote end that --delta-base-offset can be used with git-pack-objects. Eventually git-repack will always provide this flag. With this, all delta base objects are now pushed before deltas that depend on them. This is a requirements for OBJ_OFS_DELTA. This is not a requirement for OBJ_REF_DELTA but always doing so makes the code simpler. Signed-off-by: Nicolas Pitre <nico@cam.org> Signed-off-by: Junio C Hamano <junkio@cox.net>
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parent
53dda6ff62
commit
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@ -60,6 +60,8 @@ static int non_empty;
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static int no_reuse_delta;
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static int local;
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static int incremental;
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static int allow_ofs_delta;
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static struct object_entry **sorted_by_sha, **sorted_by_type;
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static struct object_entry *objects;
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static int nr_objects, nr_alloc, nr_result;
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@ -334,9 +336,6 @@ static unsigned long write_object(struct sha1file *f,
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enum object_type obj_type;
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int to_reuse = 0;
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if (entry->preferred_base)
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return 0;
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obj_type = entry->type;
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if (! entry->in_pack)
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to_reuse = 0; /* can't reuse what we don't have */
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@ -380,18 +379,35 @@ static unsigned long write_object(struct sha1file *f,
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if (entry->delta) {
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buf = delta_against(buf, size, entry);
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size = entry->delta_size;
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obj_type = OBJ_REF_DELTA;
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obj_type = (allow_ofs_delta && entry->delta->offset) ?
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OBJ_OFS_DELTA : OBJ_REF_DELTA;
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}
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/*
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* The object header is a byte of 'type' followed by zero or
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* more bytes of length. For deltas, the 20 bytes of delta
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* sha1 follows that.
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* more bytes of length.
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*/
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hdrlen = encode_header(obj_type, size, header);
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sha1write(f, header, hdrlen);
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if (entry->delta) {
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sha1write(f, entry->delta, 20);
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if (obj_type == OBJ_OFS_DELTA) {
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/*
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* Deltas with relative base contain an additional
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* encoding of the relative offset for the delta
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* base from this object's position in the pack.
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*/
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unsigned long ofs = entry->offset - entry->delta->offset;
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unsigned pos = sizeof(header) - 1;
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header[pos] = ofs & 127;
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while (ofs >>= 7)
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header[--pos] = 128 | (--ofs & 127);
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sha1write(f, header + pos, sizeof(header) - pos);
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hdrlen += sizeof(header) - pos;
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} else if (obj_type == OBJ_REF_DELTA) {
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/*
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* Deltas with a base reference contain
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* an additional 20 bytes for the base sha1.
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*/
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sha1write(f, entry->delta->sha1, 20);
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hdrlen += 20;
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}
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datalen = sha1write_compressed(f, buf, size);
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@ -413,7 +429,7 @@ static unsigned long write_object(struct sha1file *f,
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reused_delta++;
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reused++;
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}
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if (obj_type == OBJ_REF_DELTA)
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if (entry->delta)
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written_delta++;
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written++;
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return hdrlen + datalen;
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@ -423,17 +439,16 @@ static unsigned long write_one(struct sha1file *f,
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struct object_entry *e,
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unsigned long offset)
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{
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if (e->offset)
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if (e->offset || e->preferred_base)
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/* offset starts from header size and cannot be zero
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* if it is written already.
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*/
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return offset;
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e->offset = offset;
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offset += write_object(f, e);
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/* if we are deltified, write out its base object. */
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/* if we are deltified, write out its base object first. */
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if (e->delta)
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offset = write_one(f, e->delta, offset);
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return offset;
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e->offset = offset;
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return offset + write_object(f, e);
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}
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static void write_pack_file(void)
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@ -1484,6 +1499,10 @@ int cmd_pack_objects(int argc, const char **argv, const char *prefix)
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no_reuse_delta = 1;
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continue;
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}
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if (!strcmp("--delta-base-offset", arg)) {
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allow_ofs_delta = no_reuse_delta = 1;
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continue;
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}
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if (!strcmp("--stdout", arg)) {
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pack_to_stdout = 1;
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continue;
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