repo: understand the `objectformat` extension

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

2 files changed, 46 insertions, 5 deletions

diff --git a/src/libgit2/repository.c b/src/libgit2/repository.c
index df41f581c..5d51be6b7 100644
--- a/src/libgit2/repository.c
+++ b/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;
+}
diff --git a/src/libgit2/repository.h b/src/libgit2/repository.h
index a488f2bf2..b1e212a32 100644
--- a/src/libgit2/repository.h
+++ b/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;