refs: set up ref consistency check infrastructure

The "struct ref_store" is the base class which contains the "be" pointer
which provides backend-specific functions whose interfaces are defined
in the "ref_storage_be". We could reuse this polymorphism to define only
one interface. For every backend, we need to provide its own function
pointer.

The interfaces defined in the `ref_storage_be` are carefully structured
in semantic. It's organized as the five parts:

1. The name and the initialization interfaces.
2. The ref transaction interfaces.
3. The ref internal interfaces (pack, rename and copy).
4. The ref filesystem interfaces.
5. The reflog related interfaces.

To keep consistent with the git-fsck(1), add a new interface named
"fsck_refs_fn" to the end of "ref_storage_be". This semantic cannot be
grouped into any above five categories. Explicitly add blank line to
make it different from others.

Last, implement placeholder functions for each ref backends.

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

1 files changed, 8 insertions, 0 deletions

diff --git a/refs.h b/refs.h
index b3e39bc257..405073621a 100644
--- a/refs.h
+++ b/refs.h
@@ -4,6 +4,7 @@
 #include "commit.h"
 #include "repository.h"
 
+struct fsck_options;
 struct object_id;
 struct ref_store;
 struct strbuf;
@@ -542,6 +543,13 @@ int refs_for_each_reflog(struct ref_store *refs, each_reflog_fn fn, void *cb_dat
 int check_refname_format(const char *refname, int flags);
 
 /*
+ * Check the reference database for consistency. Return 0 if refs and
+ * reflogs are consistent, and non-zero otherwise. The errors will be
+ * written to stderr.
+ */
+int refs_fsck(struct ref_store *refs, struct fsck_options *o);
+
+/*
  * Apply the rules from check_refname_format, but mutate the result until it
  * is acceptable, and place the result in "out".
  */