1 files changed, 54 insertions, 16 deletions

diff --git a/refs/refs-internal.h b/refs/refs-internal.h
index 3d46131efb..192f9f85c9 100644
--- a/refs/refs-internal.h
+++ b/refs/refs-internal.h
@@ -130,13 +130,13 @@ struct ref_update {
 	/*
 	 * If (flags & REF_HAVE_NEW), set the reference to this value:
 	 */
-	unsigned char new_sha1[20];
+	struct object_id new_oid;
 
 	/*
 	 * If (flags & REF_HAVE_OLD), check that the reference
 	 * previously had this value:
 	 */
-	unsigned char old_sha1[20];
+	struct object_id old_oid;
 
 	/*
 	 * One or more of REF_HAVE_NEW, REF_HAVE_OLD, REF_NODEREF,
@@ -170,6 +170,14 @@ int refs_read_raw_ref(struct ref_store *ref_store,
 		      struct strbuf *referent, unsigned int *type);
 
 /*
+ * Write an error to `err` and return a nonzero value iff the same
+ * refname appears multiple times in `refnames`. `refnames` must be
+ * sorted on entry to this function.
+ */
+int ref_update_reject_duplicates(struct string_list *refnames,
+				 struct strbuf *err);
+
+/*
  * Add a ref_update with the specified properties to transaction, and
  * return a pointer to the new object. This function does not verify
  * that refname is well-formed. new_sha1 and old_sha1 are only
@@ -185,17 +193,27 @@ struct ref_update *ref_transaction_add_update(
 
 /*
  * Transaction states.
- * OPEN:   The transaction is in a valid state and can accept new updates.
- *         An OPEN transaction can be committed.
- * CLOSED: A closed transaction is no longer active and no other operations
- *         than free can be used on it in this state.
- *         A transaction can either become closed by successfully committing
- *         an active transaction or if there is a failure while building
- *         the transaction thus rendering it failed/inactive.
+ *
+ * OPEN:   The transaction is initialized and new updates can still be
+ *         added to it. An OPEN transaction can be prepared,
+ *         committed, freed, or aborted (freeing and aborting an open
+ *         transaction are equivalent).
+ *
+ * PREPARED: ref_transaction_prepare(), which locks all of the
+ *         references involved in the update and checks that the
+ *         update has no errors, has been called successfully for the
+ *         transaction. A PREPARED transaction can be committed or
+ *         aborted.
+ *
+ * CLOSED: The transaction is no longer active. A transaction becomes
+ *         CLOSED if there is a failure while building the transaction
+ *         or if a transaction is committed or aborted. A CLOSED
+ *         transaction can only be freed.
  */
 enum ref_transaction_state {
-	REF_TRANSACTION_OPEN   = 0,
-	REF_TRANSACTION_CLOSED = 1
+	REF_TRANSACTION_OPEN     = 0,
+	REF_TRANSACTION_PREPARED = 1,
+	REF_TRANSACTION_CLOSED   = 2
 };
 
 /*
@@ -482,6 +500,10 @@ struct ref_store;
 #define REF_STORE_WRITE		(1 << 1) /* can perform update operations */
 #define REF_STORE_ODB		(1 << 2) /* has access to object database */
 #define REF_STORE_MAIN		(1 << 3)
+#define REF_STORE_ALL_CAPS	(REF_STORE_READ | \
+				 REF_STORE_WRITE | \
+				 REF_STORE_ODB | \
+				 REF_STORE_MAIN)
 
 /*
  * Initialize the ref_store for the specified gitdir. These functions
@@ -493,6 +515,18 @@ typedef struct ref_store *ref_store_init_fn(const char *gitdir,
 
 typedef int ref_init_db_fn(struct ref_store *refs, struct strbuf *err);
 
+typedef int ref_transaction_prepare_fn(struct ref_store *refs,
+				       struct ref_transaction *transaction,
+				       struct strbuf *err);
+
+typedef int ref_transaction_finish_fn(struct ref_store *refs,
+				      struct ref_transaction *transaction,
+				      struct strbuf *err);
+
+typedef int ref_transaction_abort_fn(struct ref_store *refs,
+				     struct ref_transaction *transaction,
+				     struct strbuf *err);
+
 typedef int ref_transaction_commit_fn(struct ref_store *refs,
 				      struct ref_transaction *transaction,
 				      struct strbuf *err);
@@ -504,16 +538,17 @@ typedef int create_symref_fn(struct ref_store *ref_store,
 			     const char *ref_target,
 			     const char *refs_heads_master,
 			     const char *logmsg);
-typedef int delete_refs_fn(struct ref_store *ref_store,
+typedef int delete_refs_fn(struct ref_store *ref_store, const char *msg,
 			   struct string_list *refnames, unsigned int flags);
 typedef int rename_ref_fn(struct ref_store *ref_store,
 			  const char *oldref, const char *newref,
 			  const char *logmsg);
 
 /*
- * Iterate over the references in the specified ref_store that are
- * within find_containing_dir(prefix). If prefix is NULL or the empty
- * string, iterate over all references in the submodule.
+ * Iterate over the references in `ref_store` whose names start with
+ * `prefix`. `prefix` is matched as a literal string, without regard
+ * for path separators. If prefix is NULL or the empty string, iterate
+ * over all references in `ref_store`.
  */
 typedef struct ref_iterator *ref_iterator_begin_fn(
 		struct ref_store *ref_store,
@@ -595,7 +630,10 @@ struct ref_storage_be {
 	const char *name;
 	ref_store_init_fn *init;
 	ref_init_db_fn *init_db;
-	ref_transaction_commit_fn *transaction_commit;
+
+	ref_transaction_prepare_fn *transaction_prepare;
+	ref_transaction_finish_fn *transaction_finish;
+	ref_transaction_abort_fn *transaction_abort;
 	ref_transaction_commit_fn *initial_transaction_commit;
 
 	pack_refs_fn *pack_refs;