builtin/clone: create the refdb with the correct object format

We're currently creating the reference database with a potentially
incorrect object format when the remote repository's object format is
different from the local default object format. This works just fine for
now because the files backend never records the object format anywhere.
But this logic will fail with any new reference backend that encodes
this information in some form either on-disk or in-memory.

The preceding commits have reshuffled code in git-clone(1) so that there
is no code path that will access the reference database before we have
detected the remote's object format. With these refactorings we can now
defer initialization of the reference database until after we have
learned the remote's object format and thus initialize it with the
correct format from the get-go.

These refactorings are required to make git-clone(1) work with the
upcoming reftable backend when cloning repositories with the SHA256
object format.

This change breaks a test in "t5550-http-fetch-dumb.sh" when cloning an
empty repository with `GIT_TEST_DEFAULT_HASH=sha256`. The test expects
the resulting hash format of the empty cloned repository to match the
default hash, but now we always end up with a sha1 repository. The
problem is that for dumb HTTP fetches, we have no easy way to figure out
the remote's hash function except for deriving it based on the hash
length of refs in `info/refs`. But as the remote repository is empty we
cannot rely on this detection mechanism.

Before the change in this commit we already initialized the repository
with the default hash function and then left it as-is. With this patch
we always use the hash function detected via the remote, where we fall
back to "sha1" in case we cannot detect it.

Neither the old nor the new behaviour are correct as we second-guess the
remote hash function in both cases. But given that this is a rather
unlikely edge case (we use the dumb HTTP protocol, the remote repository
uses SHA256 and the remote repository is empty), let's simply adapt the
test to assert the new behaviour. If we want to properly address this
edge case in the future we will have to extend the dumb HTTP protocol so
that we can properly detect the hash function for empty repositories.

Signed-off-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

diff --git a/builtin/clone.c b/builtin/clone.c
index 06966c5d4c25c56c53c6f6fd93c6ddf50ab07d78..fd052b8b54372978ec61af207ee21c4fe7529013 100644 (file)
--- a/builtin/clone.c
+++ b/builtin/clone.c
@@ -1097,8 +1097,14 @@ int cmd_clone(int argc, const char **argv, const char *prefix)
                }
        }
 
+       /*
+        * Initialize the repository, but skip initializing the reference
+        * database. We do not yet know about the object format of the
+        * repository, and reference backends may persist that information into
+        * their on-disk data structures.
+        */
        init_db(git_dir, real_git_dir, option_template, GIT_HASH_UNKNOWN, NULL,
-               do_not_override_repo_unix_permissions, INIT_DB_QUIET);
+               do_not_override_repo_unix_permissions, INIT_DB_QUIET | INIT_DB_SKIP_REFDB);
 
        if (real_git_dir) {
                free((char *)git_dir);
@@ -1282,6 +1288,7 @@ int cmd_clone(int argc, const char **argv, const char *prefix)
        hash_algo = hash_algo_by_ptr(transport_get_hash_algo(transport));
        initialize_repository_version(hash_algo, 1);
        repo_set_hash_algo(the_repository, hash_algo);
+       create_reference_database(NULL, 1);
 
        /*
         * Before fetching from the remote, download and install bundle

diff --git a/setup.c b/setup.c
index d6a1c59b7bd915e8779bb28c0bcc3847fee9e830..155fe13f701c7a5e861711bfd29a7941f5382a2e 100644 (file)
--- a/setup.c
+++ b/setup.c
@@ -1897,7 +1897,7 @@ static int is_reinit(void)
        return ret;
 }
 
-static void create_reference_database(const char *initial_branch, int quiet)
+void create_reference_database(const char *initial_branch, int quiet)
 {
        struct strbuf err = STRBUF_INIT;
        int reinit = is_reinit();

diff --git a/setup.h b/setup.h
index cbf538286bfefc53d5a99e48f4932b5c53c830b7..3f0f17c351cbc54348ef1abe6b6e74a54d98ec56 100644 (file)
--- a/setup.h
+++ b/setup.h
@@ -178,6 +178,7 @@ int init_db(const char *git_dir, const char *real_git_dir,
            const char *initial_branch, int init_shared_repository,
            unsigned int flags);
 void initialize_repository_version(int hash_algo, int reinit);
+void create_reference_database(const char *initial_branch, int quiet);
 
 /*
  * NOTE NOTE NOTE!!

diff --git a/t/t5550-http-fetch-dumb.sh b/t/t5550-http-fetch-dumb.sh
index e444b30bf6156817fa624a9a3c9ed7127e61c3e1..4c3b32785d580fb32846306df720629aee9b3a4b 100755 (executable)
--- a/t/t5550-http-fetch-dumb.sh
+++ b/t/t5550-http-fetch-dumb.sh
@@ -66,11 +66,11 @@ test_expect_success 'create empty remote repository' '
        setup_post_update_server_info_hook "$HTTPD_DOCUMENT_ROOT_PATH/empty.git"
 '
 
-test_expect_success 'empty dumb HTTP repository has default hash algorithm' '
+test_expect_success 'empty dumb HTTP repository falls back to SHA1' '
        test_when_finished "rm -fr clone-empty" &&
        git clone $HTTPD_URL/dumb/empty.git clone-empty &&
        git -C clone-empty rev-parse --show-object-format >empty-format &&
-       test "$(cat empty-format)" = "$(test_oid algo)"
+       test "$(cat empty-format)" = sha1
 '
 
 setup_askpass_helper