refs: introduce "initial" transaction flag

There are two different ways to commit a transaction:

  - `ref_transaction_commit()` can be used to commit a regular
    transaction and is what almost every caller wants.

  - `initial_ref_transaction_commit()` can be used when it is known that
    the ref store that the transaction is committed for is empty and
    when there are no concurrent processes. This is used when cloning a
    new repository.

Implementing this via two separate functions has a couple of downsides.
First, every reference backend needs to implement a separate callback
even in the case where they don't special-case the initial transaction.
Second, backends are basically forced to reimplement the whole logic for
how to commit the transaction like the "files" backend does, even though
backends may wish to only tweak certain behaviour of a "normal" commit.
Third, it is awkward that callers must never prepare the transaction as
this is somewhat different than how a transaction typically works.

Refactor the code such that we instead mark initial transactions via a
separate flag when starting the transaction. This addresses all of the
mentioned painpoints, where the most important part is that it will
allow backends to have way more leeway in how exactly they want to
handle the initial transaction.

Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 0 insertions, 13 deletions

diff --git a/refs/debug.c b/refs/debug.c
index 45e2e784a0..cbac62c8a4 100644
--- a/refs/debug.c
+++ b/refs/debug.c
@@ -118,18 +118,6 @@ static int debug_transaction_abort(struct ref_store *refs,
 	return res;
 }
 
-static int debug_initial_transaction_commit(struct ref_store *refs,
-					    struct ref_transaction *transaction,
-					    struct strbuf *err)
-{
-	struct debug_ref_store *drefs = (struct debug_ref_store *)refs;
-	int res;
-	transaction->ref_store = drefs->refs;
-	res = drefs->refs->be->initial_transaction_commit(drefs->refs,
-							  transaction, err);
-	return res;
-}
-
 static int debug_pack_refs(struct ref_store *ref_store, struct pack_refs_opts *opts)
 {
 	struct debug_ref_store *drefs = (struct debug_ref_store *)ref_store;
@@ -443,7 +431,6 @@ struct ref_storage_be refs_be_debug = {
 	.transaction_prepare = debug_transaction_prepare,
 	.transaction_finish = debug_transaction_finish,
 	.transaction_abort = debug_transaction_abort,
-	.initial_transaction_commit = debug_initial_transaction_commit,
 
 	.pack_refs = debug_pack_refs,
 	.rename_ref = debug_rename_ref,