Merge branch 'ps/avoid-unnecessary-hook-invocation-with-packed-refs'

Because a deletion of ref would need to remove it from both the
loose ref store and the packed ref store, a delete-ref operation
that logically removes one ref may end up invoking ref-transaction
hook twice, which has been corrected.

* ps/avoid-unnecessary-hook-invocation-with-packed-refs:
  refs: skip hooks when deleting uncovered packed refs
  refs: do not execute reference-transaction hook on packing refs
  refs: demonstrate excessive execution of the reference-transaction hook
  refs: allow skipping the reference-transaction hook
  refs: allow passing flags when beginning transactions
  refs: extract packed_refs_delete_refs() to allow control of transaction

refs.h

@@ -226,7 +226,7 @@ char *repo_default_branch_name(struct repository *r, int quiet);
  *         struct strbuf err = STRBUF_INIT;
  *         int ret = 0;
  *
- *         transaction = ref_store_transaction_begin(refs, &err);
+ *         transaction = ref_store_transaction_begin(refs, 0, &err);
  *         if (!transaction ||
  *             ref_transaction_update(...) ||
  *             ref_transaction_create(...) ||
@@ -563,11 +563,17 @@ enum action_on_err {
 	UPDATE_REFS_QUIET_ON_ERR
 };
 
+/*
+ * Skip executing the reference-transaction hook.
+ */
+#define REF_TRANSACTION_SKIP_HOOK (1 << 0)
+
 /*
  * Begin a reference transaction.  The reference transaction must
  * be freed by calling ref_transaction_free().
  */
 struct ref_transaction *ref_store_transaction_begin(struct ref_store *refs,
+						    unsigned int flags,
 						    struct strbuf *err);
 struct ref_transaction *ref_transaction_begin(struct strbuf *err);