diff --git a/Makefile b/Makefile
index 6d45093089d..6dfe88322dd 100644
--- a/Makefile
+++ b/Makefile
@@ -1041,6 +1041,7 @@ LIB_OBJS += gpg-interface.o
 LIB_OBJS += graph.o
 LIB_OBJS += grep.o
 LIB_OBJS += hash-lookup.o
+LIB_OBJS += hash.o
 LIB_OBJS += hashmap.o
 LIB_OBJS += help.o
 LIB_OBJS += hex.o
diff --git a/hash.c b/hash.c
new file mode 100644
index 00000000000..dd5ac9d0eb2
--- /dev/null
+++ b/hash.c
@@ -0,0 +1,283 @@
+#define USE_THE_REPOSITORY_VARIABLE
+#define DISABLE_SIGN_COMPARE_WARNINGS
+
+#include "git-compat-util.h"
+#include "hash.h"
+#include "hex.h"
+
+static const struct object_id empty_tree_oid = {
+	.hash = {
+		0x4b, 0x82, 0x5d, 0xc6, 0x42, 0xcb, 0x6e, 0xb9, 0xa0, 0x60,
+		0xe5, 0x4b, 0xf8, 0xd6, 0x92, 0x88, 0xfb, 0xee, 0x49, 0x04
+	},
+	.algo = GIT_HASH_SHA1,
+};
+static const struct object_id empty_blob_oid = {
+	.hash = {
+		0xe6, 0x9d, 0xe2, 0x9b, 0xb2, 0xd1, 0xd6, 0x43, 0x4b, 0x8b,
+		0x29, 0xae, 0x77, 0x5a, 0xd8, 0xc2, 0xe4, 0x8c, 0x53, 0x91
+	},
+	.algo = GIT_HASH_SHA1,
+};
+static const struct object_id null_oid_sha1 = {
+	.hash = {0},
+	.algo = GIT_HASH_SHA1,
+};
+static const struct object_id empty_tree_oid_sha256 = {
+	.hash = {
+		0x6e, 0xf1, 0x9b, 0x41, 0x22, 0x5c, 0x53, 0x69, 0xf1, 0xc1,
+		0x04, 0xd4, 0x5d, 0x8d, 0x85, 0xef, 0xa9, 0xb0, 0x57, 0xb5,
+		0x3b, 0x14, 0xb4, 0xb9, 0xb9, 0x39, 0xdd, 0x74, 0xde, 0xcc,
+		0x53, 0x21
+	},
+	.algo = GIT_HASH_SHA256,
+};
+static const struct object_id empty_blob_oid_sha256 = {
+	.hash = {
+		0x47, 0x3a, 0x0f, 0x4c, 0x3b, 0xe8, 0xa9, 0x36, 0x81, 0xa2,
+		0x67, 0xe3, 0xb1, 0xe9, 0xa7, 0xdc, 0xda, 0x11, 0x85, 0x43,
+		0x6f, 0xe1, 0x41, 0xf7, 0x74, 0x91, 0x20, 0xa3, 0x03, 0x72,
+		0x18, 0x13
+	},
+	.algo = GIT_HASH_SHA256,
+};
+static const struct object_id null_oid_sha256 = {
+	.hash = {0},
+	.algo = GIT_HASH_SHA256,
+};
+
+static void git_hash_sha1_init(struct git_hash_ctx *ctx)
+{
+	ctx->algop = &hash_algos[GIT_HASH_SHA1];
+	git_SHA1_Init(&ctx->state.sha1);
+}
+
+static void git_hash_sha1_clone(struct git_hash_ctx *dst, const struct git_hash_ctx *src)
+{
+	dst->algop = src->algop;
+	git_SHA1_Clone(&dst->state.sha1, &src->state.sha1);
+}
+
+static void git_hash_sha1_update(struct git_hash_ctx *ctx, const void *data, size_t len)
+{
+	git_SHA1_Update(&ctx->state.sha1, data, len);
+}
+
+static void git_hash_sha1_final(unsigned char *hash, struct git_hash_ctx *ctx)
+{
+	git_SHA1_Final(hash, &ctx->state.sha1);
+}
+
+static void git_hash_sha1_final_oid(struct object_id *oid, struct git_hash_ctx *ctx)
+{
+	git_SHA1_Final(oid->hash, &ctx->state.sha1);
+	memset(oid->hash + GIT_SHA1_RAWSZ, 0, GIT_MAX_RAWSZ - GIT_SHA1_RAWSZ);
+	oid->algo = GIT_HASH_SHA1;
+}
+
+static void git_hash_sha1_init_unsafe(struct git_hash_ctx *ctx)
+{
+	ctx->algop = unsafe_hash_algo(&hash_algos[GIT_HASH_SHA1]);
+	git_SHA1_Init_unsafe(&ctx->state.sha1_unsafe);
+}
+
+static void git_hash_sha1_clone_unsafe(struct git_hash_ctx *dst, const struct git_hash_ctx *src)
+{
+	dst->algop = src->algop;
+	git_SHA1_Clone_unsafe(&dst->state.sha1_unsafe, &src->state.sha1_unsafe);
+}
+
+static void git_hash_sha1_update_unsafe(struct git_hash_ctx *ctx, const void *data,
+				      size_t len)
+{
+	git_SHA1_Update_unsafe(&ctx->state.sha1_unsafe, data, len);
+}
+
+static void git_hash_sha1_final_unsafe(unsigned char *hash, struct git_hash_ctx *ctx)
+{
+	git_SHA1_Final_unsafe(hash, &ctx->state.sha1_unsafe);
+}
+
+static void git_hash_sha1_final_oid_unsafe(struct object_id *oid, struct git_hash_ctx *ctx)
+{
+	git_SHA1_Final_unsafe(oid->hash, &ctx->state.sha1_unsafe);
+	memset(oid->hash + GIT_SHA1_RAWSZ, 0, GIT_MAX_RAWSZ - GIT_SHA1_RAWSZ);
+	oid->algo = GIT_HASH_SHA1;
+}
+
+static void git_hash_sha256_init(struct git_hash_ctx *ctx)
+{
+	ctx->algop = unsafe_hash_algo(&hash_algos[GIT_HASH_SHA256]);
+	git_SHA256_Init(&ctx->state.sha256);
+}
+
+static void git_hash_sha256_clone(struct git_hash_ctx *dst, const struct git_hash_ctx *src)
+{
+	dst->algop = src->algop;
+	git_SHA256_Clone(&dst->state.sha256, &src->state.sha256);
+}
+
+static void git_hash_sha256_update(struct git_hash_ctx *ctx, const void *data, size_t len)
+{
+	git_SHA256_Update(&ctx->state.sha256, data, len);
+}
+
+static void git_hash_sha256_final(unsigned char *hash, struct git_hash_ctx *ctx)
+{
+	git_SHA256_Final(hash, &ctx->state.sha256);
+}
+
+static void git_hash_sha256_final_oid(struct object_id *oid, struct git_hash_ctx *ctx)
+{
+	git_SHA256_Final(oid->hash, &ctx->state.sha256);
+	/*
+	 * This currently does nothing, so the compiler should optimize it out,
+	 * but keep it in case we extend the hash size again.
+	 */
+	memset(oid->hash + GIT_SHA256_RAWSZ, 0, GIT_MAX_RAWSZ - GIT_SHA256_RAWSZ);
+	oid->algo = GIT_HASH_SHA256;
+}
+
+static void git_hash_unknown_init(struct git_hash_ctx *ctx UNUSED)
+{
+	BUG("trying to init unknown hash");
+}
+
+static void git_hash_unknown_clone(struct git_hash_ctx *dst UNUSED,
+				   const struct git_hash_ctx *src UNUSED)
+{
+	BUG("trying to clone unknown hash");
+}
+
+static void git_hash_unknown_update(struct git_hash_ctx *ctx UNUSED,
+				    const void *data UNUSED,
+				    size_t len UNUSED)
+{
+	BUG("trying to update unknown hash");
+}
+
+static void git_hash_unknown_final(unsigned char *hash UNUSED,
+				   struct git_hash_ctx *ctx UNUSED)
+{
+	BUG("trying to finalize unknown hash");
+}
+
+static void git_hash_unknown_final_oid(struct object_id *oid UNUSED,
+				       struct git_hash_ctx *ctx UNUSED)
+{
+	BUG("trying to finalize unknown hash");
+}
+
+static const struct git_hash_algo sha1_unsafe_algo = {
+	.name = "sha1",
+	.format_id = GIT_SHA1_FORMAT_ID,
+	.rawsz = GIT_SHA1_RAWSZ,
+	.hexsz = GIT_SHA1_HEXSZ,
+	.blksz = GIT_SHA1_BLKSZ,
+	.init_fn = git_hash_sha1_init_unsafe,
+	.clone_fn = git_hash_sha1_clone_unsafe,
+	.update_fn = git_hash_sha1_update_unsafe,
+	.final_fn = git_hash_sha1_final_unsafe,
+	.final_oid_fn = git_hash_sha1_final_oid_unsafe,
+	.empty_tree = &empty_tree_oid,
+	.empty_blob = &empty_blob_oid,
+	.null_oid = &null_oid_sha1,
+};
+
+const struct git_hash_algo hash_algos[GIT_HASH_NALGOS] = {
+	{
+		.name = NULL,
+		.format_id = 0x00000000,
+		.rawsz = 0,
+		.hexsz = 0,
+		.blksz = 0,
+		.init_fn = git_hash_unknown_init,
+		.clone_fn = git_hash_unknown_clone,
+		.update_fn = git_hash_unknown_update,
+		.final_fn = git_hash_unknown_final,
+		.final_oid_fn = git_hash_unknown_final_oid,
+		.empty_tree = NULL,
+		.empty_blob = NULL,
+		.null_oid = NULL,
+	},
+	{
+		.name = "sha1",
+		.format_id = GIT_SHA1_FORMAT_ID,
+		.rawsz = GIT_SHA1_RAWSZ,
+		.hexsz = GIT_SHA1_HEXSZ,
+		.blksz = GIT_SHA1_BLKSZ,
+		.init_fn = git_hash_sha1_init,
+		.clone_fn = git_hash_sha1_clone,
+		.update_fn = git_hash_sha1_update,
+		.final_fn = git_hash_sha1_final,
+		.final_oid_fn = git_hash_sha1_final_oid,
+		.unsafe = &sha1_unsafe_algo,
+		.empty_tree = &empty_tree_oid,
+		.empty_blob = &empty_blob_oid,
+		.null_oid = &null_oid_sha1,
+	},
+	{
+		.name = "sha256",
+		.format_id = GIT_SHA256_FORMAT_ID,
+		.rawsz = GIT_SHA256_RAWSZ,
+		.hexsz = GIT_SHA256_HEXSZ,
+		.blksz = GIT_SHA256_BLKSZ,
+		.init_fn = git_hash_sha256_init,
+		.clone_fn = git_hash_sha256_clone,
+		.update_fn = git_hash_sha256_update,
+		.final_fn = git_hash_sha256_final,
+		.final_oid_fn = git_hash_sha256_final_oid,
+		.empty_tree = &empty_tree_oid_sha256,
+		.empty_blob = &empty_blob_oid_sha256,
+		.null_oid = &null_oid_sha256,
+	}
+};
+
+const struct object_id *null_oid(void)
+{
+	return the_hash_algo->null_oid;
+}
+
+const char *empty_tree_oid_hex(const struct git_hash_algo *algop)
+{
+	static char buf[GIT_MAX_HEXSZ + 1];
+	return oid_to_hex_r(buf, algop->empty_tree);
+}
+
+int hash_algo_by_name(const char *name)
+{
+	int i;
+	if (!name)
+		return GIT_HASH_UNKNOWN;
+	for (i = 1; i < GIT_HASH_NALGOS; i++)
+		if (!strcmp(name, hash_algos[i].name))
+			return i;
+	return GIT_HASH_UNKNOWN;
+}
+
+int hash_algo_by_id(uint32_t format_id)
+{
+	int i;
+	for (i = 1; i < GIT_HASH_NALGOS; i++)
+		if (format_id == hash_algos[i].format_id)
+			return i;
+	return GIT_HASH_UNKNOWN;
+}
+
+int hash_algo_by_length(int len)
+{
+	int i;
+	for (i = 1; i < GIT_HASH_NALGOS; i++)
+		if (len == hash_algos[i].rawsz)
+			return i;
+	return GIT_HASH_UNKNOWN;
+}
+
+const struct git_hash_algo *unsafe_hash_algo(const struct git_hash_algo *algop)
+{
+	/* If we have a faster "unsafe" implementation, use that. */
+	if (algop->unsafe)
+		return algop->unsafe;
+	/* Otherwise use the default one. */
+	return algop;
+}
diff --git a/meson.build b/meson.build
index 021a182135f..38568344953 100644
--- a/meson.build
+++ b/meson.build
@@ -311,6 +311,7 @@ libgit_sources = [
   'graph.c',
   'grep.c',
   'hash-lookup.c',
+  'hash.c',
   'hashmap.c',
   'help.c',
   'hex.c',
diff --git a/object-file.c b/object-file.c
index b0e237a2acc..de603e2ca8c 100644
--- a/object-file.c
+++ b/object-file.c
@@ -45,283 +45,6 @@
 /* The maximum size for an object header. */
 #define MAX_HEADER_LEN 32
 
-static const struct object_id empty_tree_oid = {
-	.hash = {
-		0x4b, 0x82, 0x5d, 0xc6, 0x42, 0xcb, 0x6e, 0xb9, 0xa0, 0x60,
-		0xe5, 0x4b, 0xf8, 0xd6, 0x92, 0x88, 0xfb, 0xee, 0x49, 0x04
-	},
-	.algo = GIT_HASH_SHA1,
-};
-static const struct object_id empty_blob_oid = {
-	.hash = {
-		0xe6, 0x9d, 0xe2, 0x9b, 0xb2, 0xd1, 0xd6, 0x43, 0x4b, 0x8b,
-		0x29, 0xae, 0x77, 0x5a, 0xd8, 0xc2, 0xe4, 0x8c, 0x53, 0x91
-	},
-	.algo = GIT_HASH_SHA1,
-};
-static const struct object_id null_oid_sha1 = {
-	.hash = {0},
-	.algo = GIT_HASH_SHA1,
-};
-static const struct object_id empty_tree_oid_sha256 = {
-	.hash = {
-		0x6e, 0xf1, 0x9b, 0x41, 0x22, 0x5c, 0x53, 0x69, 0xf1, 0xc1,
-		0x04, 0xd4, 0x5d, 0x8d, 0x85, 0xef, 0xa9, 0xb0, 0x57, 0xb5,
-		0x3b, 0x14, 0xb4, 0xb9, 0xb9, 0x39, 0xdd, 0x74, 0xde, 0xcc,
-		0x53, 0x21
-	},
-	.algo = GIT_HASH_SHA256,
-};
-static const struct object_id empty_blob_oid_sha256 = {
-	.hash = {
-		0x47, 0x3a, 0x0f, 0x4c, 0x3b, 0xe8, 0xa9, 0x36, 0x81, 0xa2,
-		0x67, 0xe3, 0xb1, 0xe9, 0xa7, 0xdc, 0xda, 0x11, 0x85, 0x43,
-		0x6f, 0xe1, 0x41, 0xf7, 0x74, 0x91, 0x20, 0xa3, 0x03, 0x72,
-		0x18, 0x13
-	},
-	.algo = GIT_HASH_SHA256,
-};
-static const struct object_id null_oid_sha256 = {
-	.hash = {0},
-	.algo = GIT_HASH_SHA256,
-};
-
-static void git_hash_sha1_init(struct git_hash_ctx *ctx)
-{
-	ctx->algop = &hash_algos[GIT_HASH_SHA1];
-	git_SHA1_Init(&ctx->state.sha1);
-}
-
-static void git_hash_sha1_clone(struct git_hash_ctx *dst, const struct git_hash_ctx *src)
-{
-	dst->algop = src->algop;
-	git_SHA1_Clone(&dst->state.sha1, &src->state.sha1);
-}
-
-static void git_hash_sha1_update(struct git_hash_ctx *ctx, const void *data, size_t len)
-{
-	git_SHA1_Update(&ctx->state.sha1, data, len);
-}
-
-static void git_hash_sha1_final(unsigned char *hash, struct git_hash_ctx *ctx)
-{
-	git_SHA1_Final(hash, &ctx->state.sha1);
-}
-
-static void git_hash_sha1_final_oid(struct object_id *oid, struct git_hash_ctx *ctx)
-{
-	git_SHA1_Final(oid->hash, &ctx->state.sha1);
-	memset(oid->hash + GIT_SHA1_RAWSZ, 0, GIT_MAX_RAWSZ - GIT_SHA1_RAWSZ);
-	oid->algo = GIT_HASH_SHA1;
-}
-
-static void git_hash_sha1_init_unsafe(struct git_hash_ctx *ctx)
-{
-	ctx->algop = unsafe_hash_algo(&hash_algos[GIT_HASH_SHA1]);
-	git_SHA1_Init_unsafe(&ctx->state.sha1_unsafe);
-}
-
-static void git_hash_sha1_clone_unsafe(struct git_hash_ctx *dst, const struct git_hash_ctx *src)
-{
-	dst->algop = src->algop;
-	git_SHA1_Clone_unsafe(&dst->state.sha1_unsafe, &src->state.sha1_unsafe);
-}
-
-static void git_hash_sha1_update_unsafe(struct git_hash_ctx *ctx, const void *data,
-				      size_t len)
-{
-	git_SHA1_Update_unsafe(&ctx->state.sha1_unsafe, data, len);
-}
-
-static void git_hash_sha1_final_unsafe(unsigned char *hash, struct git_hash_ctx *ctx)
-{
-	git_SHA1_Final_unsafe(hash, &ctx->state.sha1_unsafe);
-}
-
-static void git_hash_sha1_final_oid_unsafe(struct object_id *oid, struct git_hash_ctx *ctx)
-{
-	git_SHA1_Final_unsafe(oid->hash, &ctx->state.sha1_unsafe);
-	memset(oid->hash + GIT_SHA1_RAWSZ, 0, GIT_MAX_RAWSZ - GIT_SHA1_RAWSZ);
-	oid->algo = GIT_HASH_SHA1;
-}
-
-static void git_hash_sha256_init(struct git_hash_ctx *ctx)
-{
-	ctx->algop = unsafe_hash_algo(&hash_algos[GIT_HASH_SHA256]);
-	git_SHA256_Init(&ctx->state.sha256);
-}
-
-static void git_hash_sha256_clone(struct git_hash_ctx *dst, const struct git_hash_ctx *src)
-{
-	dst->algop = src->algop;
-	git_SHA256_Clone(&dst->state.sha256, &src->state.sha256);
-}
-
-static void git_hash_sha256_update(struct git_hash_ctx *ctx, const void *data, size_t len)
-{
-	git_SHA256_Update(&ctx->state.sha256, data, len);
-}
-
-static void git_hash_sha256_final(unsigned char *hash, struct git_hash_ctx *ctx)
-{
-	git_SHA256_Final(hash, &ctx->state.sha256);
-}
-
-static void git_hash_sha256_final_oid(struct object_id *oid, struct git_hash_ctx *ctx)
-{
-	git_SHA256_Final(oid->hash, &ctx->state.sha256);
-	/*
-	 * This currently does nothing, so the compiler should optimize it out,
-	 * but keep it in case we extend the hash size again.
-	 */
-	memset(oid->hash + GIT_SHA256_RAWSZ, 0, GIT_MAX_RAWSZ - GIT_SHA256_RAWSZ);
-	oid->algo = GIT_HASH_SHA256;
-}
-
-static void git_hash_unknown_init(struct git_hash_ctx *ctx UNUSED)
-{
-	BUG("trying to init unknown hash");
-}
-
-static void git_hash_unknown_clone(struct git_hash_ctx *dst UNUSED,
-				   const struct git_hash_ctx *src UNUSED)
-{
-	BUG("trying to clone unknown hash");
-}
-
-static void git_hash_unknown_update(struct git_hash_ctx *ctx UNUSED,
-				    const void *data UNUSED,
-				    size_t len UNUSED)
-{
-	BUG("trying to update unknown hash");
-}
-
-static void git_hash_unknown_final(unsigned char *hash UNUSED,
-				   struct git_hash_ctx *ctx UNUSED)
-{
-	BUG("trying to finalize unknown hash");
-}
-
-static void git_hash_unknown_final_oid(struct object_id *oid UNUSED,
-				       struct git_hash_ctx *ctx UNUSED)
-{
-	BUG("trying to finalize unknown hash");
-}
-
-static const struct git_hash_algo sha1_unsafe_algo = {
-	.name = "sha1",
-	.format_id = GIT_SHA1_FORMAT_ID,
-	.rawsz = GIT_SHA1_RAWSZ,
-	.hexsz = GIT_SHA1_HEXSZ,
-	.blksz = GIT_SHA1_BLKSZ,
-	.init_fn = git_hash_sha1_init_unsafe,
-	.clone_fn = git_hash_sha1_clone_unsafe,
-	.update_fn = git_hash_sha1_update_unsafe,
-	.final_fn = git_hash_sha1_final_unsafe,
-	.final_oid_fn = git_hash_sha1_final_oid_unsafe,
-	.empty_tree = &empty_tree_oid,
-	.empty_blob = &empty_blob_oid,
-	.null_oid = &null_oid_sha1,
-};
-
-const struct git_hash_algo hash_algos[GIT_HASH_NALGOS] = {
-	{
-		.name = NULL,
-		.format_id = 0x00000000,
-		.rawsz = 0,
-		.hexsz = 0,
-		.blksz = 0,
-		.init_fn = git_hash_unknown_init,
-		.clone_fn = git_hash_unknown_clone,
-		.update_fn = git_hash_unknown_update,
-		.final_fn = git_hash_unknown_final,
-		.final_oid_fn = git_hash_unknown_final_oid,
-		.empty_tree = NULL,
-		.empty_blob = NULL,
-		.null_oid = NULL,
-	},
-	{
-		.name = "sha1",
-		.format_id = GIT_SHA1_FORMAT_ID,
-		.rawsz = GIT_SHA1_RAWSZ,
-		.hexsz = GIT_SHA1_HEXSZ,
-		.blksz = GIT_SHA1_BLKSZ,
-		.init_fn = git_hash_sha1_init,
-		.clone_fn = git_hash_sha1_clone,
-		.update_fn = git_hash_sha1_update,
-		.final_fn = git_hash_sha1_final,
-		.final_oid_fn = git_hash_sha1_final_oid,
-		.unsafe = &sha1_unsafe_algo,
-		.empty_tree = &empty_tree_oid,
-		.empty_blob = &empty_blob_oid,
-		.null_oid = &null_oid_sha1,
-	},
-	{
-		.name = "sha256",
-		.format_id = GIT_SHA256_FORMAT_ID,
-		.rawsz = GIT_SHA256_RAWSZ,
-		.hexsz = GIT_SHA256_HEXSZ,
-		.blksz = GIT_SHA256_BLKSZ,
-		.init_fn = git_hash_sha256_init,
-		.clone_fn = git_hash_sha256_clone,
-		.update_fn = git_hash_sha256_update,
-		.final_fn = git_hash_sha256_final,
-		.final_oid_fn = git_hash_sha256_final_oid,
-		.empty_tree = &empty_tree_oid_sha256,
-		.empty_blob = &empty_blob_oid_sha256,
-		.null_oid = &null_oid_sha256,
-	}
-};
-
-const struct object_id *null_oid(void)
-{
-	return the_hash_algo->null_oid;
-}
-
-const char *empty_tree_oid_hex(const struct git_hash_algo *algop)
-{
-	static char buf[GIT_MAX_HEXSZ + 1];
-	return oid_to_hex_r(buf, algop->empty_tree);
-}
-
-int hash_algo_by_name(const char *name)
-{
-	int i;
-	if (!name)
-		return GIT_HASH_UNKNOWN;
-	for (i = 1; i < GIT_HASH_NALGOS; i++)
-		if (!strcmp(name, hash_algos[i].name))
-			return i;
-	return GIT_HASH_UNKNOWN;
-}
-
-int hash_algo_by_id(uint32_t format_id)
-{
-	int i;
-	for (i = 1; i < GIT_HASH_NALGOS; i++)
-		if (format_id == hash_algos[i].format_id)
-			return i;
-	return GIT_HASH_UNKNOWN;
-}
-
-int hash_algo_by_length(int len)
-{
-	int i;
-	for (i = 1; i < GIT_HASH_NALGOS; i++)
-		if (len == hash_algos[i].rawsz)
-			return i;
-	return GIT_HASH_UNKNOWN;
-}
-
-const struct git_hash_algo *unsafe_hash_algo(const struct git_hash_algo *algop)
-{
-	/* If we have a faster "unsafe" implementation, use that. */
-	if (algop->unsafe)
-		return algop->unsafe;
-	/* Otherwise use the default one. */
-	return algop;
-}
-
 /*
  * This is meant to hold a *small* number of objects that you would
  * want repo_read_object_file() to be able to return, but yet you do not want
