[RFC PATCH 1/3] merge-ort.c: finalize ODB transactions after each step

[Taylor Blau <me@ttaylorr.com>]

In a previous commit, the ORT merge backend learned how to use the
bulk-checkin mechanism to emit a single pack containing any new objects
created during the merge. This functionality was implemented by setting
up a new ODB transaction, and finalizing it at the end of the merge via
`process_entries()`.

In a future commit, we will extend this functionality to the new `git
replay` command, which needs to see objects from previous steps in order
to replay each commit.

As a step towards implementing this, teach the ORT backend to flush the
ODB transaction at the end of each step in `process_entries()`, and then
finalize the result with `end_odb_transaction()` when calling
`merge_finalize()`.

For normal `merge-tree --write-pack` invocations, this produces no
functional change: the pack is written out at the end of
`process_entries()`, and then the `end_odb_transaction()` call is a
noop.

Signed-off-by: Taylor Blau <me@ttaylorr.com>
---
 merge-ort.c | 5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/merge-ort.c b/merge-ort.c
index 523577d71e..7b352451cc 100644
--- a/merge-ort.c
+++ b/merge-ort.c
@@ -4354,7 +4354,7 @@ static int process_entries(struct merge_options *opt,
 		ret = -1;
 
 	if (opt->write_pack)
-		end_odb_transaction();
+		flush_odb_transaction();
 
 cleanup:
 	string_list_clear(&plist, 0);
@@ -4726,6 +4726,9 @@ void merge_switch_to_result(struct merge_options *opt,
 void merge_finalize(struct merge_options *opt,
 		    struct merge_result *result)
 {
+	if (opt->write_pack)
+		end_odb_transaction();
+
 	if (opt->renormalize)
 		git_attr_set_direction(GIT_ATTR_CHECKIN);
 	assert(opt->priv == NULL);
-- 
2.42.0.446.g0b9ef90488