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, 0 deletions

diff --git a/refs/refs-internal.h b/refs/refs-internal.h
index c7d2a6e50b..4fb8fdb872 100644
--- a/refs/refs-internal.h
+++ b/refs/refs-internal.h
@@ -389,6 +389,7 @@ struct ref_store;
  * the ref_store and to record the ref_store for later lookup.
  */
 typedef struct ref_store *ref_store_init_fn(struct repository *repo,
+					    const char *payload,
 					    const char *gitdir,
 					    unsigned int flags);
 /*
@@ -666,4 +667,17 @@ enum ref_transaction_error refs_verify_refnames_available(struct ref_store *refs
 					  unsigned int initial_transaction,
 					  struct strbuf *err);
 
+/*
+ * Given a gitdir and the reference storage payload provided, retrieve the
+ * 'refdir' and 'ref_common_dir'. The former is where references should be
+ * stored for the current worktree, the latter is the common reference
+ * directory if working with a linked worktree. If working with the main
+ * worktree, both values will be the same.
+ *
+ * This is used by backends that store references in the repository directly.
+ */
+void refs_compute_filesystem_location(const char *gitdir, const char *payload,
+				      bool *is_worktree, struct strbuf *refdir,
+				      struct strbuf *ref_common_dir);
+
 #endif /* REFS_REFS_INTERNAL_H */