Function midx_needs_update

midx-write.c:1147–1229

}

static bool midx_needs_update(struct multi_pack_index *midx, struct write_midx_context *ctx)
{
	struct strset packs = STRSET_INIT;
	struct strbuf buf = STRBUF_INIT;
	bool needed = true;

	/*
	 * Ensure that we have a valid checksum before consulting the
	 * existing MIDX in order to determine if we can avoid an
	 * update.
	 *
	 * This is necessary because the given MIDX is loaded directly
	 * from the object store (because we still compare our proposed
	 * update to any on-disk MIDX regardless of whether or not we
	 * have assigned "ctx.m") and is thus not guaranteed to have a
	 * valid checksum.
	 */
	if (!midx_checksum_valid(midx))
		goto out;

	/*
	 * If the version differs, we need to update.
	 */
	if (midx->version != ctx->version)
		goto out;

	/*
	 * Ignore incremental updates for now. The assumption is that any
	 * incremental update would be either empty (in which case we will bail
	 * out later) or it would actually cover at least one new pack.
	 */
	if (ctx->incremental)
		goto out;

	if (ctx->compact)
		goto out; /* Compaction always requires an update. */

	/*
	 * Otherwise, we need to verify that the packs covered by the existing
	 * MIDX match the packs that we already have. The logic to do so is way
	 * more complicated than it has any right to be. This is because:
	 *
	 *   - We cannot assume any ordering.
	 *
	 *   - The MIDX packs may not be loaded at all, and loading them would
	 *     be wasteful. So we need to use the pack names tracked by the
	 *     MIDX itself.
	 *
	 *   - The MIDX pack names are tracking the ".idx" files, whereas the
	 *     packs themselves are tracking the ".pack" files. So we need to
	 *     strip suffixes.
	 */
	if (ctx->nr != midx->num_packs + midx->num_packs_in_base)
		goto out;

	for (uint32_t i = 0; i < ctx->nr; i++) {
		strbuf_reset(&buf);
		strbuf_addstr(&buf, pack_basename(ctx->info[i].p));