Re: [PATCH v6? 08/17] refs file-backend.c: stop setting "EBUSY" in verify_lock()

This EBUSY was set in 835e3c992fd (refs.c: verify_lock should set
errno to something meaningful, 2014-06-20) to fix a bug in code that
was later refactored in cd94f765720 (fetch.c: change s_update_ref to
use a ref transaction, 2014-04-28) to not use errno at all, the two
were a part of the same series.

So this was only ever needed for an intra-series bugfix, and we kept
it around for no reason. Removing it makes subsequent commits where we
refactor code surrounding verify_lock() (which may use errno) easier
to reason about.

diff --git a/refs/files-backend.c b/refs/files-backend.c
index a4e9344ac8b..abed0572fea 100644
--- a/refs/files-backend.c
+++ b/refs/files-backend.c

@@ -880,9 +880,7 @@ static int verify_lock(struct ref_store *ref_store, struct ref_lock *lock,
                               mustexist ? RESOLVE_REF_READING : 0,
                               &lock->old_oid, NULL)) {
                if (old_oid) {
-                       int save_errno = errno;
                        strbuf_addf(err, "can't verify ref '%s'", lock->ref_name);
-                       errno = save_errno;