[PATCH v2 1/2] midx: apply gitconfig to midx repack

["Son Luong Ngoc via GitGitGadget" <gitgitgadget@gmail.com>]

From: Son Luong Ngoc <sluongng@gmail.com>

Multi-Pack-Index repack is an incremental, repack solutions
that allows user to consolidate multiple packfiles in a non-disruptive
way. However the new packfile could be created without some of the
capabilities of a packfile that is created by calling `git repack`.

This is because with `git repack`, there are configuration that would
enable different flags to be passed down to `git pack-objects` plumbing.

In this patch, I applies those flags into `git multi-pack-index repack`
so that it respect the `repack.*` config series.

Note:
- `repack.packKeptObjects` will be addressed by Derrick Stolee in
the following patch
- `repack.writeBitmaps` when `--batch-size=0` was NOT adopted here as it
requires `--all` to be passed onto `git pack-objects`, which is very
slow. I think it would be nice to have this in a future patch.

Signed-off-by: Son Luong Ngoc <sluongng@gmail.com>
---
 midx.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/midx.c b/midx.c
index 9a61d3b37d9..3348f8e569b 100644
--- a/midx.c
+++ b/midx.c
@@ -1369,6 +1369,8 @@ int midx_repack(struct repository *r, const char *object_dir, size_t batch_size,
 	struct child_process cmd = CHILD_PROCESS_INIT;
 	struct strbuf base_name = STRBUF_INIT;
 	struct multi_pack_index *m = load_multi_pack_index(object_dir, 1);
+	int delta_base_offset = 1;
+	int use_delta_islands;
 
 	if (!m)
 		return 0;
@@ -1381,12 +1383,20 @@ int midx_repack(struct repository *r, const char *object_dir, size_t batch_size,
 	} else if (fill_included_packs_all(m, include_pack))
 		goto cleanup;
 
+	repo_config_get_bool(r, "repack.usedeltabaseoffset", &delta_base_offset);
+	repo_config_get_bool(r, "repack.usedeltaislands", &use_delta_islands);
+
 	argv_array_push(&cmd.args, "pack-objects");
 
 	strbuf_addstr(&base_name, object_dir);
 	strbuf_addstr(&base_name, "/pack/pack");
 	argv_array_push(&cmd.args, base_name.buf);
 
+	if (delta_base_offset)
+		argv_array_push(&cmd.args, "--delta-base-offset");
+	if (use_delta_islands)
+		argv_array_push(&cmd.args, "--delta-islands");
+
 	if (flags & MIDX_PROGRESS)
 		argv_array_push(&cmd.args, "--progress");
 	else
-- 
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