repo: understand the objectformat extension

Teach the repository about the `objectformat` extension, supporting
`sha1` always and `sha256` when the experimental sha256 support is
active.

include/git2/repository.h

@@ -949,6 +949,14 @@ GIT_EXTERN(int) git_repository_ident(const char **name, const char **email, cons
  */
 GIT_EXTERN(int) git_repository_set_ident(git_repository *repo, const char *name, const char *email);
 
+/**
+ * Gets the object type used by this repository.
+ *
+ * @param repo the repository
+ * @return the object id type
+ */
+GIT_EXTERN(git_oid_t) git_repository_oid_type(git_repository *repo);
+
 /** @} */
 GIT_END_DECL
 #endif

src/libgit2/repository.c

@@ -67,6 +67,7 @@ static const struct {
 static int check_repositoryformatversion(int *version, git_config *config);
 static int check_extensions(git_config *config, int version);
 static int load_global_config(git_config **config);
+static int load_objectformat(git_repository *repo, git_config *config);
 
 #define GIT_COMMONDIR_FILE "commondir"
 #define GIT_GITDIR_FILE "gitdir"
@@ -240,7 +241,7 @@ GIT_INLINE(int) validate_repo_path(git_str *path)
 	 */
 	static size_t suffix_len =
 		CONST_STRLEN("objects/pack/pack-.pack.lock") +
-		GIT_OID_SHA1_HEXSIZE;
+		GIT_OID_MAX_HEXSIZE;
 
 	return git_fs_path_validate_str_length_with_suffix(
 		path, suffix_len);
@@ -1030,6 +1031,13 @@ int git_repository_open_ext(
 			goto cleanup;
 	}
 
+	if (version > 0) {
+		if ((error = load_objectformat(repo, config)) < 0)
+			goto cleanup;
+	} else {
+		repo->oid_type = GIT_OID_SHA1;
+	}
+
 	/*
 	 * Ensure that the git directory and worktree are
 	 * owned by the current user.
@@ -1549,7 +1557,8 @@ static int check_repositoryformatversion(int *version, git_config *config)
 }
 
 static const char *builtin_extensions[] = {
-	"noop"
+	"noop",
+	"objectformat"
 };
 
 static git_vector user_extensions = GIT_VECTOR_INIT;
@@ -1613,6 +1622,32 @@ static int check_extensions(git_config *config, int version)
 	return git_config_foreach_match(config, "^extensions\\.", check_valid_extension, NULL);
 }
 
+static int load_objectformat(git_repository *repo, git_config *config)
+{
+	git_config_entry *entry = NULL;
+	int error;
+
+	if ((error = git_config_get_entry(&entry, config, "extensions.objectformat")) < 0) {
+		if (error == GIT_ENOTFOUND) {
+			repo->oid_type = GIT_OID_SHA1;
+			git_error_clear();
+			error = 0;
+		}
+
+		goto done;
+	}
+
+	if ((repo->oid_type = git_oid_type_fromstr(entry->value)) == 0) {
+		git_error_set(GIT_ERROR_REPOSITORY,
+			"unknown object format '%s'", entry->value);
+		error = GIT_EINVALID;
+	}
+
+done:
+	git_config_entry_free(entry);
+	return error;
+}
+
 int git_repository__extensions(char ***out, size_t *out_len)
 {
 	git_vector extensions;
@@ -2922,14 +2957,14 @@ int git_repository__set_orig_head(git_repository *repo, const git_oid *orig_head
 {
 	git_filebuf file = GIT_FILEBUF_INIT;
 	git_str file_path = GIT_STR_INIT;
-	char orig_head_str[GIT_OID_SHA1_HEXSIZE];
+	char orig_head_str[GIT_OID_MAX_HEXSIZE];
 	int error = 0;
 
 	git_oid_fmt(orig_head_str, orig_head);
 
 	if ((error = git_str_joinpath(&file_path, repo->gitdir, GIT_ORIG_HEAD_FILE)) == 0 &&
 		(error = git_filebuf_open(&file, file_path.ptr, GIT_FILEBUF_CREATE_LEADING_DIRS, GIT_MERGE_FILE_MODE)) == 0 &&
-		(error = git_filebuf_printf(&file, "%.*s\n", GIT_OID_SHA1_HEXSIZE, orig_head_str)) == 0)
+		(error = git_filebuf_printf(&file, "%.*s\n", (int)git_oid_hexsize(repo->oid_type), orig_head_str)) == 0)
 		error = git_filebuf_commit(&file);
 
 	if (error < 0)
@@ -3042,7 +3077,7 @@ int git_repository_hashfile(
 		goto cleanup;
 	}
 
-	error = git_odb__hashfd_filtered(out, fd, (size_t)len, type, GIT_OID_SHA1, fl);
+	error = git_odb__hashfd_filtered(out, fd, (size_t)len, type, repo->oid_type, fl);
 
 cleanup:
 	if (fd >= 0)
@@ -3389,3 +3424,8 @@ int git_repository_submodule_cache_clear(git_repository *repo)
 	repo->submodule_cache = NULL;
 	return error;
 }
+
+git_oid_t git_repository_oid_type(git_repository *repo)
+{
+	return repo ? repo->oid_type : 0;
+}

src/libgit2/repository.h

@@ -153,6 +153,7 @@ struct git_repository {
 
 	unsigned is_bare:1;
 	unsigned is_worktree:1;
+	git_oid_t oid_type;
 
 	unsigned int lru_counter;
 

tests/libgit2/core/opts.c

@@ -34,8 +34,9 @@ void test_core_opts__extensions_query(void)
 
 	cl_git_pass(git_libgit2_opts(GIT_OPT_GET_EXTENSIONS, &out));
 
-	cl_assert_equal_sz(out.count, 1);
+	cl_assert_equal_sz(out.count, 2);
 	cl_assert_equal_s("noop", out.strings[0]);
+	cl_assert_equal_s("objectformat", out.strings[1]);
 
 	git_strarray_dispose(&out);
 }
@@ -48,9 +49,10 @@ void test_core_opts__extensions_add(void)
 	cl_git_pass(git_libgit2_opts(GIT_OPT_SET_EXTENSIONS, in, ARRAY_SIZE(in)));
 	cl_git_pass(git_libgit2_opts(GIT_OPT_GET_EXTENSIONS, &out));
 
-	cl_assert_equal_sz(out.count, 2);
+	cl_assert_equal_sz(out.count, 3);
 	cl_assert_equal_s("noop", out.strings[0]);
-	cl_assert_equal_s("foo", out.strings[1]);
+	cl_assert_equal_s("objectformat", out.strings[1]);
+	cl_assert_equal_s("foo", out.strings[2]);
 
 	git_strarray_dispose(&out);
 }
@@ -63,9 +65,10 @@ void test_core_opts__extensions_remove(void)
 	cl_git_pass(git_libgit2_opts(GIT_OPT_SET_EXTENSIONS, in, ARRAY_SIZE(in)));
 	cl_git_pass(git_libgit2_opts(GIT_OPT_GET_EXTENSIONS, &out));
 
-	cl_assert_equal_sz(out.count, 2);
-	cl_assert_equal_s("bar", out.strings[0]);
-	cl_assert_equal_s("baz", out.strings[1]);
+	cl_assert_equal_sz(out.count, 3);
+	cl_assert_equal_s("objectformat", out.strings[0]);
+	cl_assert_equal_s("bar", out.strings[1]);
+	cl_assert_equal_s("baz", out.strings[2]);
 
 	git_strarray_dispose(&out);
 }

tests/libgit2/repo/objectformat.c

@@ -0,0 +1,69 @@
+#include "clar_libgit2.h"
+#include "futils.h"
+#include "sysdir.h"
+#include "repository.h"
+#include <ctype.h>
+
+git_repository *repo;
+git_config *config;
+
+void test_repo_objectformat__initialize(void)
+{
+	repo = cl_git_sandbox_init("empty_bare.git");
+
+	cl_git_pass(git_repository_config(&config, repo));
+	cl_git_pass(git_config_set_int32(config, "core.repositoryformatversion", 1));
+}
+
+void test_repo_objectformat__cleanup(void)
+{
+	git_config_free(config);
+	cl_git_sandbox_cleanup();
+}
+
+void test_repo_objectformat__unspecified(void)
+{
+	git_repository *other;
+
+	cl_git_pass(git_repository_open(&other, "empty_bare.git"));
+	cl_assert_equal_i(GIT_OID_SHA1, git_repository_oid_type(other));
+	git_repository_free(other);
+}
+
+void test_repo_objectformat__sha1(void)
+{
+	git_repository *other;
+
+	cl_git_pass(git_config_set_string(config, "extensions.objectformat", "sha1"));
+
+	cl_git_pass(git_repository_open(&other, "empty_bare.git"));
+	cl_assert_equal_i(GIT_OID_SHA1, git_repository_oid_type(other));
+	git_repository_free(other);
+}
+
+void test_repo_objectformat__sha256(void)
+{
+#ifndef GIT_EXPERIMENTAL_SHA256
+	cl_skip();
+#else
+	git_repository *other;
+
+	cl_git_pass(git_config_set_string(config, "extensions.objectformat", "sha256"));
+
+	cl_git_pass(git_repository_open(&other, "empty_bare.git"));
+	cl_assert_equal_i(GIT_OID_SHA256, git_repository_oid_type(other));
+	git_repository_free(other);
+#endif
+}
+
+void test_repo_objectformat__invalid(void)
+{
+	git_repository *other;
+
+	cl_git_pass(git_config_set_string(config, "extensions.objectformat", "bogus"));
+
+	cl_git_fail_with(GIT_EINVALID, git_repository_open(&other, "empty_bare.git"));
+	cl_assert_equal_s("unknown object format 'bogus'", git_error_last()->message);
+	git_repository_free(other);
+}
+