[PATCH v5 4/5] bulk-checkin: introduce `index_tree_bulk_checkin_incore()`

From: Taylor Blau <me@ttaylorr.com>
Date: Oct 23, 2023, 22:45 UTC
Message-ID: <2670192802a904b42fb0c11c26c9f7311aa8dd90.1698101088.git.me@ttaylorr.com>
In-Reply-To: <cover.1698101088.git.me@ttaylorr.com>

The remaining missing piece in order to teach the `merge-tree` builtin how to write the contents of a merge into a pack is a function to index tree objects into a bulk-checkin pack.

This patch implements that missing piece, which is a thin wrapper around all of the functionality introduced in previous commits.

If and when Git gains support for a "compatibility" hash algorithm, the changes to support that here will be minimal. The bulk-checkin machinery will need to convert the incoming tree to compute its length under the compatibility hash, necessary to reconstruct its header. With that information (and the converted contents of the tree), the bulk-checkin machinery will have enough to keep track of the converted object's hash in order to update the compatibility mapping.

Within some thin wrapper around `deflate_obj_to_pack_incore()` (perhaps `deflate_tree_to_pack_incore()`), the changes should be limited to something like:

    struct strbuf converted = STRBUF_INIT;
    if (the_repository->compat_hash_algo) {
      if (convert_object_file(&compat_obj,
                              the_repository->hash_algo,
                              the_repository->compat_hash_algo, ...) < 0)
        die(...);

      format_object_header_hash(the_repository->compat_hash_algo,
                                OBJ_TREE, size);
    }
    /* compute the converted tree's hash using the compat algorithm */
    strbuf_release(&converted);

, assuming related changes throughout the rest of the bulk-checkin machinery necessary to update the hash of the converted object, which are likewise minimal in size.

Signed-off-by: Taylor Blau <me@ttaylorr.com>
---
 bulk-checkin.c | 12 ++++++++++++
 bulk-checkin.h |  4 ++++
 2 files changed, 16 insertions(+)

diff --git a/bulk-checkin.c b/bulk-checkin.c
index b728210bc7..bd6151ba3c 100644
--- a/bulk-checkin.c
+++ b/bulk-checkin.c
@@ -496,6 +496,18 @@ int index_blob_bulk_checkin_incore(struct object_id *oid,
 	return status;
 }
 
+int index_tree_bulk_checkin_incore(struct object_id *oid,
+				   const void *buf, size_t size,
+				   const char *path, unsigned flags)
+{
+	int status = deflate_obj_to_pack_incore(&bulk_checkin_packfile, oid,
+						buf, size, path, OBJ_TREE,
+						flags);
+	if (!odb_transaction_nesting)
+		flush_bulk_checkin_packfile(&bulk_checkin_packfile);
+	return status;
+}
+
 void begin_odb_transaction(void)
 {
 	odb_transaction_nesting += 1;
diff --git a/bulk-checkin.h b/bulk-checkin.h
index 1b91daeaee..89786b3954 100644
--- a/bulk-checkin.h
+++ b/bulk-checkin.h
@@ -17,6 +17,10 @@ int index_blob_bulk_checkin_incore(struct object_id *oid,
 				   const void *buf, size_t size,
 				   const char *path, unsigned flags);
 
+int index_tree_bulk_checkin_incore(struct object_id *oid,
+				   const void *buf, size_t size,
+				   const char *path, unsigned flags);
+
 /*
  * Tell the object database to optimize for adding
  * multiple objects. end_odb_transaction must be called

-- 
2.42.0.425.g963d08ddb3.dirty