refs: receive and use the reference storage payload

An upcoming commit will add support for providing an URI via the
'extensions.refStorage' config. The URI will contain the reference
backend and a corresponding payload. The payload can be then used for
providing an alternate locations for the reference backend.

To prepare for this, modify the existing backends to accept such an
argument when initializing via the 'init()' function. Both the files
and reftable backends will parse the information to be filesystem paths
to store references. Given that no callers pass any payload yet this is
essentially a no-op change for now.

To enable this, provide a 'refs_compute_filesystem_location()' function
which will parse the current 'gitdir' and the 'payload' to provide the
final reference directory and common reference directory (if working in
a linked worktree).

The documentation and tests will be added alongside the extension of the
config variable.

Helped-by: Patrick Steinhardt <ps@pks.im>
Signed-off-by: Karthik Nayak <karthik.188@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 14 insertions, 10 deletions

diff --git a/refs/reftable-backend.c b/refs/reftable-backend.c
index 6ce7f9bb8e..0e220d6bb5 100644
--- a/refs/reftable-backend.c
+++ b/refs/reftable-backend.c
@@ -372,18 +372,24 @@ static int reftable_be_fsync(int fd)
 }
 
 static struct ref_store *reftable_be_init(struct repository *repo,
+					  const char *payload,
 					  const char *gitdir,
 					  unsigned int store_flags)
 {
 	struct reftable_ref_store *refs = xcalloc(1, sizeof(*refs));
+	struct strbuf ref_common_dir = STRBUF_INIT;
+	struct strbuf refdir = STRBUF_INIT;
 	struct strbuf path = STRBUF_INIT;
-	int is_worktree;
+	bool is_worktree;
 	mode_t mask;
 
 	mask = umask(0);
 	umask(mask);
 
-	base_ref_store_init(&refs->base, repo, gitdir, &refs_be_reftable);
+	refs_compute_filesystem_location(gitdir, payload, &is_worktree, &refdir,
+					 &ref_common_dir);
+
+	base_ref_store_init(&refs->base, repo, refdir.buf, &refs_be_reftable);
 	strmap_init(&refs->worktree_backends);
 	refs->store_flags = store_flags;
 	refs->log_all_ref_updates = repo_settings_get_log_all_ref_updates(repo);
@@ -419,14 +425,11 @@ static struct ref_store *reftable_be_init(struct repository *repo,
 	/*
 	 * Set up the main reftable stack that is hosted in GIT_COMMON_DIR.
 	 * This stack contains both the shared and the main worktree refs.
-	 *
-	 * Note that we don't try to resolve the path in case we have a
-	 * worktree because `get_common_dir_noenv()` already does it for us.
 	 */
-	is_worktree = get_common_dir_noenv(&path, gitdir);
+	strbuf_addbuf(&path, &ref_common_dir);
 	if (!is_worktree) {
 		strbuf_reset(&path);
-		strbuf_realpath(&path, gitdir, 0);
+		strbuf_realpath(&path, ref_common_dir.buf, 0);
 	}
 	strbuf_addstr(&path, "/reftable");
 	refs->err = reftable_backend_init(&refs->main_backend, path.buf,
@@ -443,10 +446,9 @@ static struct ref_store *reftable_be_init(struct repository *repo,
 	 * do it efficiently.
 	 */
 	if (is_worktree) {
-		strbuf_reset(&path);
-		strbuf_addf(&path, "%s/reftable", gitdir);
+		strbuf_addstr(&refdir, "/reftable");
 
-		refs->err = reftable_backend_init(&refs->worktree_backend, path.buf,
+		refs->err = reftable_backend_init(&refs->worktree_backend, refdir.buf,
 						  &refs->write_options);
 		if (refs->err)
 			goto done;
@@ -456,6 +458,8 @@ static struct ref_store *reftable_be_init(struct repository *repo,
 
 done:
 	assert(refs->err != REFTABLE_API_ERROR);
+	strbuf_release(&ref_common_dir);
+	strbuf_release(&refdir);
 	strbuf_release(&path);
 	return &refs->base;
 }