diff --git a/builtin/multi-pack-index.c b/builtin/multi-pack-index.c
index 85e40a4b6d3e47..2a938466f53aaa 100644
--- a/builtin/multi-pack-index.c
+++ b/builtin/multi-pack-index.c
@@ -120,7 +120,7 @@ static void read_packs_from_stdin(struct string_list *to)
 
 static int cmd_multi_pack_index_write(int argc, const char **argv,
 				      const char *prefix,
-				      struct repository *repo UNUSED)
+				      struct repository *repo)
 {
 	struct option *options;
 	static struct option builtin_multi_pack_index_write_options[] = {
@@ -165,7 +165,7 @@ static int cmd_multi_pack_index_write(int argc, const char **argv,
 
 		read_packs_from_stdin(&packs);
 
-		ret = write_midx_file_only(opts.object_dir, &packs,
+		ret = write_midx_file_only(repo, opts.object_dir, &packs,
 					   opts.preferred_pack,
 					   opts.refs_snapshot, opts.flags);
 
@@ -176,7 +176,7 @@ static int cmd_multi_pack_index_write(int argc, const char **argv,
 
 	}
 
-	ret = write_midx_file(opts.object_dir, opts.preferred_pack,
+	ret = write_midx_file(repo, opts.object_dir, opts.preferred_pack,
 			      opts.refs_snapshot, opts.flags);
 
 	free(opts.refs_snapshot);
diff --git a/builtin/repack.c b/builtin/repack.c
index 02a40212ffb25b..ae266bba92ae24 100644
--- a/builtin/repack.c
+++ b/builtin/repack.c
@@ -1576,7 +1576,7 @@ int cmd_repack(int argc,
 		unsigned flags = 0;
 		if (git_env_bool(GIT_TEST_MULTI_PACK_INDEX_WRITE_INCREMENTAL, 0))
 			flags |= MIDX_WRITE_INCREMENTAL;
-		write_midx_file(repo_get_object_directory(the_repository),
+		write_midx_file(the_repository, repo_get_object_directory(the_repository),
 				NULL, NULL, flags);
 	}
 
diff --git a/midx-write.c b/midx-write.c
index 6cf5f9042f3824..46014f911bb52a 100644
--- a/midx-write.c
+++ b/midx-write.c
@@ -1,5 +1,3 @@
-#define USE_THE_REPOSITORY_VARIABLE
-
 #include "git-compat-util.h"
 #include "abspath.h"
 #include "config.h"
@@ -35,13 +33,13 @@ extern void clear_incremental_midx_files_ext(const char *object_dir,
 extern int cmp_idx_or_pack_name(const char *idx_or_pack_name,
 				const char *idx_name);
 
-static size_t write_midx_header(struct hashfile *f,
-				unsigned char num_chunks,
+static size_t write_midx_header(const struct git_hash_algo *hash_algo,
+				struct hashfile *f, unsigned char num_chunks,
 				uint32_t num_packs)
 {
 	hashwrite_be32(f, MIDX_SIGNATURE);
 	hashwrite_u8(f, MIDX_VERSION);
-	hashwrite_u8(f, oid_version(the_hash_algo));
+	hashwrite_u8(f, oid_version(hash_algo));
 	hashwrite_u8(f, num_chunks);
 	hashwrite_u8(f, 0); /* unused */
 	hashwrite_be32(f, num_packs);
@@ -110,6 +108,8 @@ struct write_midx_context {
 	uint32_t num_multi_pack_indexes_before;
 
 	struct string_list *to_include;
+
+	struct repository *repo;
 };
 
 static int should_include_pack(const struct write_midx_context *ctx,
@@ -154,7 +154,7 @@ static void add_pack_to_midx(const char *full_path, size_t full_path_len,
 			return;
 
 		ALLOC_GROW(ctx->info, ctx->nr + 1, ctx->alloc);
-		p = add_packed_git(the_repository, full_path, full_path_len, 0);
+		p = add_packed_git(ctx->repo, full_path, full_path_len, 0);
 		if (!p) {
 			warning(_("failed to add packfile '%s'"),
 				full_path);
@@ -480,7 +480,7 @@ static int write_midx_oid_lookup(struct hashfile *f,
 				 void *data)
 {
 	struct write_midx_context *ctx = data;
-	unsigned char hash_len = the_hash_algo->rawsz;
+	unsigned char hash_len = ctx->repo->hash_algo->rawsz;
 	struct pack_midx_entry *list = ctx->entries;
 	uint32_t i;
 
@@ -605,7 +605,7 @@ static uint32_t *midx_pack_order(struct write_midx_context *ctx)
 	uint32_t *pack_order, base_objects = 0;
 	uint32_t i;
 
-	trace2_region_enter("midx", "midx_pack_order", the_repository);
+	trace2_region_enter("midx", "midx_pack_order", ctx->repo);
 
 	if (ctx->incremental && ctx->base_midx)
 		base_objects = ctx->base_midx->num_objects +
@@ -640,7 +640,7 @@ static uint32_t *midx_pack_order(struct write_midx_context *ctx)
 	}
 	free(data);
 
-	trace2_region_leave("midx", "midx_pack_order", the_repository);
+	trace2_region_leave("midx", "midx_pack_order", ctx->repo);
 
 	return pack_order;
 }
@@ -652,13 +652,15 @@ static void write_midx_reverse_index(struct write_midx_context *ctx,
 	struct strbuf buf = STRBUF_INIT;
 	char *tmp_file;
 
-	trace2_region_enter("midx", "write_midx_reverse_index", the_repository);
+	trace2_region_enter("midx", "write_midx_reverse_index", ctx->repo);
 
 	if (ctx->incremental)
-		get_split_midx_filename_ext(&buf, object_dir, midx_hash,
+		get_split_midx_filename_ext(ctx->repo->hash_algo,
+					    &buf, object_dir, midx_hash,
 					    MIDX_EXT_REV);
 	else
-		get_midx_filename_ext(&buf, object_dir, midx_hash,
+		get_midx_filename_ext(ctx->repo->hash_algo,
+				      &buf, object_dir, midx_hash,
 				      MIDX_EXT_REV);
 
 	tmp_file = write_rev_file_order(NULL, ctx->pack_order, ctx->entries_nr,
@@ -670,7 +672,7 @@ static void write_midx_reverse_index(struct write_midx_context *ctx,
 	strbuf_release(&buf);
 	free(tmp_file);
 
-	trace2_region_leave("midx", "write_midx_reverse_index", the_repository);
+	trace2_region_leave("midx", "write_midx_reverse_index", ctx->repo);
 }
 
 static void prepare_midx_packing_data(struct packing_data *pdata,
@@ -678,10 +680,10 @@ static void prepare_midx_packing_data(struct packing_data *pdata,
 {
 	uint32_t i;
 
-	trace2_region_enter("midx", "prepare_midx_packing_data", the_repository);
+	trace2_region_enter("midx", "prepare_midx_packing_data", ctx->repo);
 
 	memset(pdata, 0, sizeof(struct packing_data));
-	prepare_packing_data(the_repository, pdata);
+	prepare_packing_data(ctx->repo, pdata);
 
 	for (i = 0; i < ctx->entries_nr; i++) {
 		uint32_t pos = ctx->pack_order[i];
@@ -692,7 +694,7 @@ static void prepare_midx_packing_data(struct packing_data *pdata,
 			       ctx->info[ctx->pack_perm[from->pack_int_id]].p);
 	}
 
-	trace2_region_leave("midx", "prepare_midx_packing_data", the_repository);
+	trace2_region_leave("midx", "prepare_midx_packing_data", ctx->repo);
 }
 
 static int add_ref_to_pending(const char *refname, const char *referent UNUSED,
@@ -708,7 +710,7 @@ static int add_ref_to_pending(const char *refname, const char *referent UNUSED,
 		return 0;
 	}
 
-	if (!peel_iterated_oid(the_repository, oid, &peeled))
+	if (!peel_iterated_oid(revs->repo, oid, &peeled))
 		oid = &peeled;
 
 	object = parse_object_or_die(oid, refname);
@@ -766,7 +768,7 @@ static int read_refs_snapshot(const char *refs_snapshot,
 			hex = &buf.buf[1];
 		}
 
-		if (parse_oid_hex(hex, &oid, &end) < 0)
+		if (parse_oid_hex_algop(hex, &oid, &end, revs->repo->hash_algo) < 0)
 			die(_("could not parse line: %s"), buf.buf);
 		if (*end)
 			die(_("malformed line: %s"), buf.buf);
@@ -782,6 +784,7 @@ static int read_refs_snapshot(const char *refs_snapshot,
 	strbuf_release(&buf);
 	return 0;
 }
+
 static struct commit **find_commits_for_midx_bitmap(uint32_t *indexed_commits_nr_p,
 						    const char *refs_snapshot,
 						    struct write_midx_context *ctx)
@@ -789,17 +792,16 @@ static struct commit **find_commits_for_midx_bitmap(uint32_t *indexed_commits_nr
 	struct rev_info revs;
 	struct bitmap_commit_cb cb = {0};
 
-	trace2_region_enter("midx", "find_commits_for_midx_bitmap",
-			    the_repository);
+	trace2_region_enter("midx", "find_commits_for_midx_bitmap", ctx->repo);
 
 	cb.ctx = ctx;
 
-	repo_init_revisions(the_repository, &revs, NULL);
+	repo_init_revisions(ctx->repo, &revs, NULL);
 	if (refs_snapshot) {
 		read_refs_snapshot(refs_snapshot, &revs);
 	} else {
 		setup_revisions(0, NULL, &revs, NULL);
-		refs_for_each_ref(get_main_ref_store(the_repository),
+		refs_for_each_ref(get_main_ref_store(ctx->repo),
 				  add_ref_to_pending, &revs);
 	}
 
@@ -827,8 +829,7 @@ static struct commit **find_commits_for_midx_bitmap(uint32_t *indexed_commits_nr
 
 	release_revisions(&revs);
 
-	trace2_region_leave("midx", "find_commits_for_midx_bitmap",
-			    the_repository);
+	trace2_region_leave("midx", "find_commits_for_midx_bitmap", ctx->repo);
 
 	return cb.commits;
 }
@@ -848,13 +849,15 @@ static int write_midx_bitmap(struct write_midx_context *ctx,
 	struct strbuf bitmap_name = STRBUF_INIT;
 
 	if (ctx->incremental)
-		get_split_midx_filename_ext(&bitmap_name, object_dir, midx_hash,
+		get_split_midx_filename_ext(ctx->repo->hash_algo,
+					    &bitmap_name, object_dir, midx_hash,
 					    MIDX_EXT_BITMAP);
 	else
-		get_midx_filename_ext(&bitmap_name, object_dir, midx_hash,
+		get_midx_filename_ext(ctx->repo->hash_algo,
+				      &bitmap_name, object_dir, midx_hash,
 				      MIDX_EXT_BITMAP);
 
-	trace2_region_enter("midx", "write_midx_bitmap", the_repository);
+	trace2_region_enter("midx", "write_midx_bitmap", ctx->repo);
 
 	if (flags & MIDX_WRITE_BITMAP_HASH_CACHE)
 		options |= BITMAP_OPT_HASH_CACHE;
@@ -871,7 +874,7 @@ static int write_midx_bitmap(struct write_midx_context *ctx,
 	for (i = 0; i < pdata->nr_objects; i++)
 		index[i] = &pdata->objects[i].idx;
 
-	bitmap_writer_init(&writer, the_repository, pdata,
+	bitmap_writer_init(&writer, ctx->repo, pdata,
 			   ctx->incremental ? ctx->base_midx : NULL);
 	bitmap_writer_show_progress(&writer, flags & MIDX_PROGRESS);
 	bitmap_writer_build_type_index(&writer, index);
@@ -905,7 +908,7 @@ static int write_midx_bitmap(struct write_midx_context *ctx,
 	strbuf_release(&bitmap_name);
 	bitmap_writer_free(&writer);
 
-	trace2_region_leave("midx", "write_midx_bitmap", the_repository);
+	trace2_region_leave("midx", "write_midx_bitmap", ctx->repo);
 
 	return ret;
 }
@@ -957,7 +960,7 @@ static int fill_packs_from_midx(struct write_midx_context *ctx,
 			 */
 			if (flags & MIDX_WRITE_REV_INDEX ||
 			    preferred_pack_name) {
-				if (prepare_midx_pack(the_repository, m,
+				if (prepare_midx_pack(ctx->repo, m,
 						      m->num_packs_in_base + i)) {
 					error(_("could not load pack"));
 					return 1;
@@ -1004,9 +1007,10 @@ static int link_midx_to_chain(struct multi_pack_index *m)
 	for (i = 0; i < ARRAY_SIZE(midx_exts); i++) {
 		const unsigned char *hash = get_midx_checksum(m);
 
-		get_midx_filename_ext(&from, m->object_dir, hash,
-				      midx_exts[i].non_split);
-		get_split_midx_filename_ext(&to, m->object_dir, hash,
+		get_midx_filename_ext(m->repo->hash_algo, &from, m->object_dir,
+				      hash, midx_exts[i].non_split);
+		get_split_midx_filename_ext(m->repo->hash_algo, &to,
+					    m->object_dir, hash,
 					    midx_exts[i].split);
 
 		if (link(from.buf, to.buf) < 0 && errno != ENOENT) {
@@ -1025,9 +1029,8 @@ static int link_midx_to_chain(struct multi_pack_index *m)
 	return ret;
 }
 
-static void clear_midx_files(const char *object_dir,
-			     const char **hashes,
-			     uint32_t hashes_nr,
+static void clear_midx_files(struct repository *r, const char *object_dir,
+			     const char **hashes, uint32_t hashes_nr,
 			     unsigned incremental)
 {
 	/*
@@ -1052,7 +1055,7 @@ static void clear_midx_files(const char *object_dir,
 	}
 
 	if (incremental)
-		get_midx_filename(&buf, object_dir);
+		get_midx_filename(r->hash_algo, &buf, object_dir);
 	else
 		get_midx_chain_filename(&buf, object_dir);
 
@@ -1062,7 +1065,7 @@ static void clear_midx_files(const char *object_dir,
 	strbuf_release(&buf);
 }
 
-static int write_midx_internal(const char *object_dir,
+static int write_midx_internal(struct repository *r, const char *object_dir,
 			       struct string_list *packs_to_include,
 			       struct string_list *packs_to_drop,
 			       const char *preferred_pack_name,
@@ -1083,7 +1086,9 @@ static int write_midx_internal(const char *object_dir,
 	const char **keep_hashes = NULL;
 	struct chunkfile *cf;
 
-	trace2_region_enter("midx", "write_midx_internal", the_repository);
+	trace2_region_enter("midx", "write_midx_internal", r);
+
+	ctx.repo = r;
 
 	ctx.incremental = !!(flags & MIDX_WRITE_INCREMENTAL);
 
@@ -1092,14 +1097,13 @@ static int write_midx_internal(const char *object_dir,
 			    "%s/pack/multi-pack-index.d/tmp_midx_XXXXXX",
 			    object_dir);
 	else
-		get_midx_filename(&midx_name, object_dir);
+		get_midx_filename(r->hash_algo, &midx_name, object_dir);
 	if (safe_create_leading_directories(midx_name.buf))
 		die_errno(_("unable to create leading directories of %s"),
 			  midx_name.buf);
 
 	if (!packs_to_include || ctx.incremental) {
-		struct multi_pack_index *m = lookup_multi_pack_index(the_repository,
-								     object_dir);
+		struct multi_pack_index *m = lookup_multi_pack_index(r, object_dir);
 		if (m && !midx_checksum_valid(m)) {
 			warning(_("ignoring existing multi-pack-index; checksum mismatch"));
 			m = NULL;
@@ -1129,7 +1133,8 @@ static int write_midx_internal(const char *object_dir,
 		while (m) {
 			if (flags & MIDX_WRITE_BITMAP && load_midx_revindex(m)) {
 				error(_("could not load reverse index for MIDX %s"),
-				      hash_to_hex(get_midx_checksum(m)));
+				      hash_to_hex_algop(get_midx_checksum(m),
+							r->hash_algo));
 				result = 1;
 				goto cleanup;
 			}
@@ -1368,7 +1373,7 @@ static int write_midx_internal(const char *object_dir,
 	add_chunk(cf, MIDX_CHUNKID_OIDFANOUT, MIDX_CHUNK_FANOUT_SIZE,
 		  write_midx_oid_fanout);
 	add_chunk(cf, MIDX_CHUNKID_OIDLOOKUP,
-		  st_mult(ctx.entries_nr, the_hash_algo->rawsz),
+		  st_mult(ctx.entries_nr, r->hash_algo->rawsz),
 		  write_midx_oid_lookup);
 	add_chunk(cf, MIDX_CHUNKID_OBJECTOFFSETS,
 		  st_mult(ctx.entries_nr, MIDX_CHUNK_OFFSET_WIDTH),
@@ -1390,7 +1395,8 @@ static int write_midx_internal(const char *object_dir,
 			  write_midx_bitmapped_packs);
 	}
 
-	write_midx_header(f, get_num_chunks(cf), ctx.nr - dropped_packs);
+	write_midx_header(r->hash_algo, f, get_num_chunks(cf),
+			  ctx.nr - dropped_packs);
 	write_chunkfile(cf, &ctx);
 
 	finalize_hashfile(f, midx_hash, FSYNC_COMPONENT_PACK_METADATA,
@@ -1455,8 +1461,8 @@ static int write_midx_internal(const char *object_dir,
 		if (link_midx_to_chain(ctx.base_midx) < 0)
 			return -1;
 
-		get_split_midx_filename_ext(&final_midx_name, object_dir,
-					    midx_hash, MIDX_EXT_MIDX);
+		get_split_midx_filename_ext(r->hash_algo, &final_midx_name,
+					    object_dir, midx_hash, MIDX_EXT_MIDX);
 
 		if (rename_tempfile(&incr, final_midx_name.buf) < 0) {
 			error_errno(_("unable to rename new multi-pack-index layer"));
@@ -1466,12 +1472,13 @@ static int write_midx_internal(const char *object_dir,
 		strbuf_release(&final_midx_name);
 
 		keep_hashes[ctx.num_multi_pack_indexes_before] =
-			xstrdup(hash_to_hex(midx_hash));
+			xstrdup(hash_to_hex_algop(midx_hash, r->hash_algo));
 
 		for (i = 0; i < ctx.num_multi_pack_indexes_before; i++) {
 			uint32_t j = ctx.num_multi_pack_indexes_before - i - 1;
 
-			keep_hashes[j] = xstrdup(hash_to_hex(get_midx_checksum(m)));
+			keep_hashes[j] = xstrdup(hash_to_hex_algop(get_midx_checksum(m),
+								   r->hash_algo));
 			m = m->base_midx;
 		}
 
@@ -1479,16 +1486,16 @@ static int write_midx_internal(const char *object_dir,
 			fprintf(get_lock_file_fp(&lk), "%s\n", keep_hashes[i]);
 	} else {
 		keep_hashes[ctx.num_multi_pack_indexes_before] =
-			xstrdup(hash_to_hex(midx_hash));
+			xstrdup(hash_to_hex_algop(midx_hash, r->hash_algo));
 	}
 
 	if (ctx.m || ctx.base_midx)
-		close_object_store(the_repository->objects);
+		close_object_store(ctx.repo->objects);
 
 	if (commit_lock_file(&lk) < 0)
 		die_errno(_("could not write multi-pack-index"));
 
-	clear_midx_files(object_dir, keep_hashes,
+	clear_midx_files(r, object_dir, keep_hashes,
 			 ctx.num_multi_pack_indexes_before + 1,
 			 ctx.incremental);
 
@@ -1512,27 +1519,26 @@ static int write_midx_internal(const char *object_dir,
 	}
 	strbuf_release(&midx_name);
 
-	trace2_region_leave("midx", "write_midx_internal", the_repository);
+	trace2_region_leave("midx", "write_midx_internal", r);
 
 	return result;
 }
 
-int write_midx_file(const char *object_dir,
+int write_midx_file(struct repository *r, const char *object_dir,
 		    const char *preferred_pack_name,
-		    const char *refs_snapshot,
-		    unsigned flags)
+		    const char *refs_snapshot, unsigned flags)
 {
-	return write_midx_internal(object_dir, NULL, NULL, preferred_pack_name,
-				   refs_snapshot, flags);
+	return write_midx_internal(r, object_dir, NULL, NULL,
+				   preferred_pack_name, refs_snapshot,
+				   flags);
 }
 
-int write_midx_file_only(const char *object_dir,
+int write_midx_file_only(struct repository *r, const char *object_dir,
 			 struct string_list *packs_to_include,
 			 const char *preferred_pack_name,
-			 const char *refs_snapshot,
-			 unsigned flags)
+			 const char *refs_snapshot, unsigned flags)
 {
-	return write_midx_internal(object_dir, packs_to_include, NULL,
+	return write_midx_internal(r, object_dir, packs_to_include, NULL,
 				   preferred_pack_name, refs_snapshot, flags);
 }
 
@@ -1589,7 +1595,8 @@ int expire_midx_packs(struct repository *r, const char *object_dir, unsigned fla
 	free(count);
 
 	if (packs_to_drop.nr)
-		result = write_midx_internal(object_dir, NULL, &packs_to_drop, NULL, NULL, flags);
+		result = write_midx_internal(r, object_dir, NULL,
+					     &packs_to_drop, NULL, NULL, flags);
 
 	string_list_clear(&packs_to_drop, 0);
 
@@ -1786,7 +1793,8 @@ int midx_repack(struct repository *r, const char *object_dir, size_t batch_size,
 		goto cleanup;
 	}
 
-	result = write_midx_internal(object_dir, NULL, NULL, NULL, NULL, flags);
+	result = write_midx_internal(r, object_dir, NULL, NULL, NULL, NULL,
+				     flags);
 
 cleanup:
 	free(include_pack);
diff --git a/midx.c b/midx.c
index 079c45a1aafb65..e0eae1c25ec91f 100644
--- a/midx.c
+++ b/midx.c
@@ -1,5 +1,3 @@
-#define USE_THE_REPOSITORY_VARIABLE
-
 #include "git-compat-util.h"
 #include "config.h"
 #include "dir.h"
@@ -25,20 +23,22 @@ int cmp_idx_or_pack_name(const char *idx_or_pack_name,
 
 const unsigned char *get_midx_checksum(struct multi_pack_index *m)
 {
-	return m->data + m->data_len - the_hash_algo->rawsz;
+	return m->data + m->data_len - m->repo->hash_algo->rawsz;
 }
 
-void get_midx_filename(struct strbuf *out, const char *object_dir)
+void get_midx_filename(const struct git_hash_algo *hash_algo,
+		       struct strbuf *out, const char *object_dir)
 {
-	get_midx_filename_ext(out, object_dir, NULL, NULL);
+	get_midx_filename_ext(hash_algo, out, object_dir, NULL, NULL);
 }
 
-void get_midx_filename_ext(struct strbuf *out, const char *object_dir,
+void get_midx_filename_ext(const struct git_hash_algo *hash_algo,
+			   struct strbuf *out, const char *object_dir,
 			   const unsigned char *hash, const char *ext)
 {
 	strbuf_addf(out, "%s/pack/multi-pack-index", object_dir);
 	if (ext)
-		strbuf_addf(out, "-%s.%s", hash_to_hex(hash), ext);
+		strbuf_addf(out, "-%s.%s", hash_to_hex_algop(hash, hash_algo), ext);
 }
 
 static int midx_read_oid_fanout(const unsigned char *chunk_start,
@@ -92,9 +92,8 @@ static int midx_read_object_offsets(const unsigned char *chunk_start,
 	return 0;
 }
 
-#define MIDX_MIN_SIZE (MIDX_HEADER_SIZE + the_hash_algo->rawsz)
-
-static struct multi_pack_index *load_multi_pack_index_one(const char *object_dir,
+static struct multi_pack_index *load_multi_pack_index_one(struct repository *r,
+							  const char *object_dir,
 							  const char *midx_name,
 							  int local)
 {
@@ -119,7 +118,7 @@ static struct multi_pack_index *load_multi_pack_index_one(const char *object_dir
 
 	midx_size = xsize_t(st.st_size);
 
-	if (midx_size < MIDX_MIN_SIZE) {
+	if (midx_size < (MIDX_HEADER_SIZE + r->hash_algo->rawsz)) {
 		error(_("multi-pack-index file %s is too small"), midx_name);
 		goto cleanup_fail;
 	}
@@ -131,7 +130,7 @@ static struct multi_pack_index *load_multi_pack_index_one(const char *object_dir
 	m->data = midx_map;
 	m->data_len = midx_size;
 	m->local = local;
-	m->repo = the_repository;
+	m->repo = r;
 
 	m->signature = get_be32(m->data);
 	if (m->signature != MIDX_SIGNATURE)
@@ -144,12 +143,12 @@ static struct multi_pack_index *load_multi_pack_index_one(const char *object_dir
 		      m->version);
 
 	hash_version = m->data[MIDX_BYTE_HASH_VERSION];
-	if (hash_version != oid_version(the_hash_algo)) {
+	if (hash_version != oid_version(r->hash_algo)) {
 		error(_("multi-pack-index hash version %u does not match version %u"),
-		      hash_version, oid_version(the_hash_algo));
+		      hash_version, oid_version(r->hash_algo));
 		goto cleanup_fail;
 	}
-	m->hash_len = the_hash_algo->rawsz;
+	m->hash_len = r->hash_algo->rawsz;
 
 	m->num_chunks = m->data[MIDX_BYTE_NUM_CHUNKS];
 
@@ -206,8 +205,8 @@ static struct multi_pack_index *load_multi_pack_index_one(const char *object_dir
 			      m->pack_names[i]);
 	}
 
-	trace2_data_intmax("midx", the_repository, "load/num_packs", m->num_packs);
-	trace2_data_intmax("midx", the_repository, "load/num_objects", m->num_objects);
+	trace2_data_intmax("midx", r, "load/num_packs", m->num_packs);
+	trace2_data_intmax("midx", r, "load/num_objects", m->num_objects);
 
 	free_chunkfile(cf);
 	return m;
@@ -233,15 +232,18 @@ void get_midx_chain_filename(struct strbuf *buf, const char *object_dir)
 	strbuf_addstr(buf, "/multi-pack-index-chain");
 }
 
-void get_split_midx_filename_ext(struct strbuf *buf, const char *object_dir,
+void get_split_midx_filename_ext(const struct git_hash_algo *hash_algo,
+				 struct strbuf *buf, const char *object_dir,
 				 const unsigned char *hash, const char *ext)
 {
 	get_midx_chain_dirname(buf, object_dir);
-	strbuf_addf(buf, "/multi-pack-index-%s.%s", hash_to_hex(hash), ext);
+	strbuf_addf(buf, "/multi-pack-index-%s.%s",
+		    hash_to_hex_algop(hash, hash_algo), ext);
 }
 
-static int open_multi_pack_index_chain(const char *chain_file,
-				       int *fd, struct stat *st)
+static int open_multi_pack_index_chain(const struct git_hash_algo *hash_algo,
+				       const char *chain_file, int *fd,
+				       struct stat *st)
 {
 	*fd = git_open(chain_file);
 	if (*fd < 0)
@@ -250,7 +252,7 @@ static int open_multi_pack_index_chain(const char *chain_file,
 		close(*fd);
 		return 0;
 	}
-	if (st->st_size < the_hash_algo->hexsz) {
+	if (st->st_size < hash_algo->hexsz) {
 		close(*fd);
 		if (!st->st_size) {
 			/* treat empty files the same as missing */
@@ -292,7 +294,8 @@ static int add_midx_to_chain(struct multi_pack_index *midx,
 	return 1;
 }
 
-static struct multi_pack_index *load_midx_chain_fd_st(const char *object_dir,
+static struct multi_pack_index *load_midx_chain_fd_st(struct repository *r,
+						      const char *object_dir,
 						      int local,
 						      int fd, struct stat *st,
 						      int *incomplete_chain)
@@ -303,7 +306,7 @@ static struct multi_pack_index *load_midx_chain_fd_st(const char *object_dir,
 	uint32_t i, count;
 	FILE *fp = xfdopen(fd, "r");
 
-	count = st->st_size / (the_hash_algo->hexsz + 1);
+	count = st->st_size / (r->hash_algo->hexsz + 1);
 
 	for (i = 0; i < count; i++) {
 		struct multi_pack_index *m;
@@ -312,7 +315,7 @@ static struct multi_pack_index *load_midx_chain_fd_st(const char *object_dir,
 		if (strbuf_getline_lf(&buf, fp) == EOF)
 			break;
 
-		if (get_oid_hex(buf.buf, &layer)) {
+		if (get_oid_hex_algop(buf.buf, &layer, r->hash_algo)) {
 			warning(_("invalid multi-pack-index chain: line '%s' "
 				  "not a hash"),
 				buf.buf);
@@ -323,9 +326,9 @@ static struct multi_pack_index *load_midx_chain_fd_st(const char *object_dir,
 		valid = 0;
 
 		strbuf_reset(&buf);
-		get_split_midx_filename_ext(&buf, object_dir, layer.hash,
-					    MIDX_EXT_MIDX);
-		m = load_multi_pack_index_one(object_dir, buf.buf, local);
+		get_split_midx_filename_ext(r->hash_algo, &buf, object_dir,
+					    layer.hash, MIDX_EXT_MIDX);
+		m = load_multi_pack_index_one(r, object_dir, buf.buf, local);
 
 		if (m) {
 			if (add_midx_to_chain(m, midx_chain)) {
@@ -348,7 +351,8 @@ static struct multi_pack_index *load_midx_chain_fd_st(const char *object_dir,
 	return midx_chain;
 }
 
-static struct multi_pack_index *load_multi_pack_index_chain(const char *object_dir,
+static struct multi_pack_index *load_multi_pack_index_chain(struct repository *r,
+							    const char *object_dir,
 							    int local)
 {
 	struct strbuf chain_file = STRBUF_INIT;
@@ -357,10 +361,10 @@ static struct multi_pack_index *load_multi_pack_index_chain(const char *object_d
 	struct multi_pack_index *m = NULL;
 
 	get_midx_chain_filename(&chain_file, object_dir);
-	if (open_multi_pack_index_chain(chain_file.buf, &fd, &st)) {
+	if (open_multi_pack_index_chain(r->hash_algo, chain_file.buf, &fd, &st)) {
 		int incomplete;
 		/* ownership of fd is taken over by load function */
-		m = load_midx_chain_fd_st(object_dir, local, fd, &st,
+		m = load_midx_chain_fd_st(r, object_dir, local, fd, &st,
 					  &incomplete);
 	}
 
@@ -368,17 +372,19 @@ static struct multi_pack_index *load_multi_pack_index_chain(const char *object_d
 	return m;
 }
 
-struct multi_pack_index *load_multi_pack_index(const char *object_dir,
+struct multi_pack_index *load_multi_pack_index(struct repository *r,
+					       const char *object_dir,
 					       int local)
 {
 	struct strbuf midx_name = STRBUF_INIT;
 	struct multi_pack_index *m;
 
-	get_midx_filename(&midx_name, object_dir);
+	get_midx_filename(r->hash_algo, &midx_name, object_dir);
 
-	m = load_multi_pack_index_one(object_dir, midx_name.buf, local);
+	m = load_multi_pack_index_one(r, object_dir,
+				      midx_name.buf, local);
 	if (!m)
-		m = load_multi_pack_index_chain(object_dir, local);
+		m = load_multi_pack_index_chain(r, object_dir, local);
 
 	strbuf_release(&midx_name);
 
@@ -520,7 +526,7 @@ int bsearch_one_midx(const struct object_id *oid, struct multi_pack_index *m,
 		     uint32_t *result)
 {
 	int ret = bsearch_hash(oid->hash, m->chunk_oid_fanout,
-			       m->chunk_oid_lookup, the_hash_algo->rawsz,
+			       m->chunk_oid_lookup, m->repo->hash_algo->rawsz,
 			       result);
 	if (result)
 		*result += m->num_objects_in_base;
@@ -551,7 +557,7 @@ struct object_id *nth_midxed_object_oid(struct object_id *oid,
 	n = midx_for_object(&m, n);
 
 	oidread(oid, m->chunk_oid_lookup + st_mult(m->hash_len, n),
-		the_repository->hash_algo);
+		m->repo->hash_algo);
 	return oid;
 }
 
@@ -722,7 +728,7 @@ int prepare_multi_pack_index_one(struct repository *r, const char *object_dir, i
 		if (!strcmp(object_dir, m_search->object_dir))
 			return 1;
 
-	m = load_multi_pack_index(object_dir, local);
+	m = load_multi_pack_index(r, object_dir, local);
 
 	if (m) {
 		struct multi_pack_index *mp = r->objects->multi_pack_index;
@@ -816,7 +822,7 @@ void clear_midx_file(struct repository *r)
 {
 	struct strbuf midx = STRBUF_INIT;
 
-	get_midx_filename(&midx, r->objects->odb->path);
+	get_midx_filename(r->hash_algo, &midx, r->objects->odb->path);
 
 	if (r->objects && r->objects->multi_pack_index) {
 		close_midx(r->objects->multi_pack_index);
@@ -876,7 +882,7 @@ int verify_midx_file(struct repository *r, const char *object_dir, unsigned flag
 	struct pair_pos_vs_id *pairs = NULL;
 	uint32_t i;
 	struct progress *progress = NULL;
-	struct multi_pack_index *m = load_multi_pack_index(object_dir, 1);
+	struct multi_pack_index *m = load_multi_pack_index(r, object_dir, 1);
 	struct multi_pack_index *curr;
 	verify_midx_error = 0;
 
@@ -885,7 +891,7 @@ int verify_midx_file(struct repository *r, const char *object_dir, unsigned flag
 		struct stat sb;
 		struct strbuf filename = STRBUF_INIT;
 
-		get_midx_filename(&filename, object_dir);
+		get_midx_filename(r->hash_algo, &filename, object_dir);
 
 		if (!stat(filename.buf, &sb)) {
 			error(_("multi-pack-index file exists, but failed to parse"));
diff --git a/midx.h b/midx.h
index 3b0ac4d8788b37..9d1374cbd58d01 100644
--- a/midx.h
+++ b/midx.h
@@ -7,6 +7,7 @@ struct object_id;
 struct pack_entry;
 struct repository;
 struct bitmapped_pack;
+struct git_hash_algo;
 
 #define MIDX_SIGNATURE 0x4d494458 /* "MIDX" */
 #define MIDX_VERSION 1
@@ -89,15 +90,20 @@ struct multi_pack_index {
 #define MIDX_EXT_MIDX "midx"
 
 const unsigned char *get_midx_checksum(struct multi_pack_index *m);
-void get_midx_filename(struct strbuf *out, const char *object_dir);
-void get_midx_filename_ext(struct strbuf *out, const char *object_dir,
+void get_midx_filename(const struct git_hash_algo *hash_algo,
+		       struct strbuf *out, const char *object_dir);
+void get_midx_filename_ext(const struct git_hash_algo *hash_algo,
+			   struct strbuf *out, const char *object_dir,
 			   const unsigned char *hash, const char *ext);
 void get_midx_chain_dirname(struct strbuf *buf, const char *object_dir);
 void get_midx_chain_filename(struct strbuf *buf, const char *object_dir);
-void get_split_midx_filename_ext(struct strbuf *buf, const char *object_dir,
+void get_split_midx_filename_ext(const struct git_hash_algo *hash_algo,
+				 struct strbuf *buf, const char *object_dir,
 				 const unsigned char *hash, const char *ext);
 
-struct multi_pack_index *load_multi_pack_index(const char *object_dir, int local);
+struct multi_pack_index *load_multi_pack_index(struct repository *r,
+					       const char *object_dir,
+					       int local);
 int prepare_midx_pack(struct repository *r, struct multi_pack_index *m, uint32_t pack_int_id);
 struct packed_git *nth_midxed_pack(struct multi_pack_index *m,
 				   uint32_t pack_int_id);
@@ -123,15 +129,13 @@ int prepare_multi_pack_index_one(struct repository *r, const char *object_dir, i
  * Variant of write_midx_file which writes a MIDX containing only the packs
  * specified in packs_to_include.
  */
-int write_midx_file(const char *object_dir,
-		    const char *preferred_pack_name,
-		    const char *refs_snapshot,
+int write_midx_file(struct repository *r, const char *object_dir,
+		    const char *preferred_pack_name, const char *refs_snapshot,
 		    unsigned flags);
-int write_midx_file_only(const char *object_dir,
+int write_midx_file_only(struct repository *r, const char *object_dir,
 			 struct string_list *packs_to_include,
 			 const char *preferred_pack_name,
-			 const char *refs_snapshot,
-			 unsigned flags);
+			 const char *refs_snapshot, unsigned flags);
 void clear_midx_file(struct repository *r);
 int verify_midx_file(struct repository *r, const char *object_dir, unsigned flags);
 int expire_midx_packs(struct repository *r, const char *object_dir, unsigned flags);
diff --git a/pack-bitmap.c b/pack-bitmap.c
index c4daeacbb1d653..a7e12f9f9ede22 100644
--- a/pack-bitmap.c
+++ b/pack-bitmap.c
@@ -409,12 +409,15 @@ static int load_bitmap_entries_v1(struct bitmap_index *index)
 char *midx_bitmap_filename(struct multi_pack_index *midx)
 {
 	struct strbuf buf = STRBUF_INIT;
+
 	if (midx->has_chain)
-		get_split_midx_filename_ext(&buf, midx->object_dir,
+		get_split_midx_filename_ext(midx->repo->hash_algo,
+					    &buf, midx->object_dir,
 					    get_midx_checksum(midx),
 					    MIDX_EXT_BITMAP);
 	else
-		get_midx_filename_ext(&buf, midx->object_dir,
+		get_midx_filename_ext(midx->repo->hash_algo,
+				      &buf, midx->object_dir,
 				      get_midx_checksum(midx), MIDX_EXT_BITMAP);
 
 	return strbuf_detach(&buf, NULL);
@@ -461,7 +464,7 @@ static int open_midx_bitmap_1(struct bitmap_index *bitmap_git,
 
 	if (bitmap_git->pack || bitmap_git->midx) {
 		struct strbuf buf = STRBUF_INIT;
-		get_midx_filename(&buf, midx->object_dir);
+		get_midx_filename(midx->repo->hash_algo, &buf, midx->object_dir);
 		trace2_data_string("bitmap", bitmap_repo(bitmap_git),
 				   "ignoring extra midx bitmap file", buf.buf);
 		close(fd);
diff --git a/pack-revindex.c b/pack-revindex.c
index ce3f7ae2149bd7..e487f27cb8a714 100644
--- a/pack-revindex.c
+++ b/pack-revindex.c
@@ -384,10 +384,12 @@ int load_midx_revindex(struct multi_pack_index *m)
 			   "source", "rev");
 
 	if (m->has_chain)
-		get_split_midx_filename_ext(&revindex_name, m->object_dir,
+		get_split_midx_filename_ext(m->repo->hash_algo,
+					    &revindex_name, m->object_dir,
 					    get_midx_checksum(m), MIDX_EXT_REV);
 	else
-		get_midx_filename_ext(&revindex_name, m->object_dir,
+		get_midx_filename_ext(m->repo->hash_algo,
+				      &revindex_name, m->object_dir,
 				      get_midx_checksum(m), MIDX_EXT_REV);
 
 	ret = load_revindex_from_disk(revindex_name.buf,
diff --git a/t/helper/test-read-midx.c b/t/helper/test-read-midx.c
index 438fb9fc6197fc..fc632369618917 100644
--- a/t/helper/test-read-midx.c
+++ b/t/helper/test-read-midx.c
@@ -18,7 +18,7 @@ static int read_midx_file(const char *object_dir, const char *checksum,
 	struct multi_pack_index *m;
 
 	setup_git_directory();
-	m = load_multi_pack_index(object_dir, 1);
+	m = load_multi_pack_index(the_repository, object_dir, 1);
 
 	if (!m)
 		return 1;
@@ -82,7 +82,7 @@ static int read_midx_checksum(const char *object_dir)
 	struct multi_pack_index *m;
 
 	setup_git_directory();
-	m = load_multi_pack_index(object_dir, 1);
+	m = load_multi_pack_index(the_repository, object_dir, 1);
 	if (!m)
 		return 1;
 	printf("%s\n", hash_to_hex(get_midx_checksum(m)));
@@ -98,7 +98,7 @@ static int read_midx_preferred_pack(const char *object_dir)
 
 	setup_git_directory();
 
-	midx = load_multi_pack_index(object_dir, 1);
+	midx = load_multi_pack_index(the_repository, object_dir, 1);
 	if (!midx)
 		return 1;
 
@@ -121,7 +121,7 @@ static int read_midx_bitmapped_packs(const char *object_dir)
 
 	setup_git_directory();
 
-	midx = load_multi_pack_index(object_dir, 1);
+	midx = load_multi_pack_index(the_repository, object_dir, 1);
 	if (!midx)
 		return 1;