refs: extract out `refs_create_refdir_stubs()`

For Git to recognize a directory as a Git directory, it requires the
directory to contain:

  1. 'HEAD' file
  2. 'objects/' directory
  3. 'refs/' directory

Here, #1 and #3 are part of the reference storage mechanism,
specifically the files backend. Since then, newer backends such as the
reftable backend have moved to using their own path ('reftable/') for
storing references. But to ensure Git still recognizes the directory as
a Git directory, we create stubs.

There are two locations where we create stubs:

- In 'refs/reftable-backend.c' when creating the reftable backend.
- In 'clone.c' before spawning transport helpers.

In a following commit, we'll add another instance. So instead of
repeating the code, let's extract out this code to
`refs_create_refdir_stubs()` and use it.

Signed-off-by: Karthik Nayak <karthik.188@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 13 insertions, 0 deletions

diff --git a/refs.h b/refs.h
index f0abfa1d93..a35fdc6642 100644
--- a/refs.h
+++ b/refs.h
@@ -1427,4 +1427,17 @@ void ref_iterator_free(struct ref_iterator *ref_iterator);
 int do_for_each_ref_iterator(struct ref_iterator *iter,
 			     each_ref_fn fn, void *cb_data);
 
+/*
+ * Git only recognizes a directory as a repository if it contains:
+ * - HEAD file
+ * - refs/ folder
+ * While it is necessary within the files backend, newer backends may not
+ * follow the same structure. To go around this, we create stubs as necessary.
+ *
+ * If provided with a 'refs_heads_content', we create the 'refs/heads/head' file
+ * with the provided message.
+ */
+void refs_create_refdir_stubs(struct repository *repo, const char *refdir,
+			      const char *refs_heads_content);
+
 #endif /* REFS_H */