[PATCH v12 16/41] refs.c: add transaction.status and track OPEN/CLOSED/ERROR

[Ronnie Sahlberg <sahlberg@google.com>]

Track the status of a transaction in a new status field. Check the field for
sanity, i.e. that status must be OPEN when _commit/_create/_delete or
_update is called or else die(BUG:...)

Signed-off-by: Ronnie Sahlberg <sahlberg@google.com>
---
 refs.c | 36 +++++++++++++++++++++++++++++++++++-
 1 file changed, 35 insertions(+), 1 deletion(-)

diff --git a/refs.c b/refs.c
index b5186cd..00d8fc9 100644
--- a/refs.c
+++ b/refs.c
@@ -3331,6 +3331,30 @@ struct ref_update {
 };
 
 /*
+ * Transaction states.
+ * OPEN:   The transaction is in a valid state and can accept new updates.
+ *         An OPEN transaction can be committed.
+ * CLOSED: If an open transaction is successfully committed the state will
+ *         change to CLOSED. No further changes can be made to a CLOSED
+ *         transaction.
+ *         CLOSED means that all updates have been successfully committed and
+ *         the only thing that remains is to free the completed transaction.
+ * ERROR:  The transaction has failed and is no longer committable.
+ *         Eventhough the transaction can no longer be committed it is still
+ *         possible to add additional updates to the transaction. The reason
+ *         for this is to allow a caller to continue trying more updates
+ *         so that a caller can report a list of ALL updates that would fail
+ *         instead of just the first update that fails.
+ *         An ERRORed transaction can not be committed and must be rolled
+ *         back using transaction_free.
+ */
+enum ref_transaction_state {
+	REF_TRANSACTION_OPEN   = 0,
+	REF_TRANSACTION_CLOSED = 1,
+	REF_TRANSACTION_ERROR  = 2,
+};
+
+/*
  * Data structure for holding a reference transaction, which can
  * consist of checks and updates to multiple references, carried out
  * as atomically as possible.  This structure is opaque to callers.
@@ -3339,6 +3363,8 @@ struct ref_transaction {
 	struct ref_update **updates;
 	size_t alloc;
 	size_t nr;
+	enum ref_transaction_state state;
+	int status;
 };
 
 struct ref_transaction *ref_transaction_begin(struct strbuf *err)
@@ -3476,8 +3502,13 @@ int ref_transaction_commit(struct ref_transaction *transaction,
 	int n = transaction->nr;
 	struct ref_update **updates = transaction->updates;
 
-	if (!n)
+	if (transaction->state != REF_TRANSACTION_OPEN)
+		return transaction->status;
+
+	if (!n) {
+		transaction->state = REF_TRANSACTION_CLOSED;
 		return 0;
+	}
 
 	/* Allocate work space */
 	delnames = xmalloc(sizeof(*delnames) * n);
@@ -3540,6 +3571,9 @@ int ref_transaction_commit(struct ref_transaction *transaction,
 	clear_loose_ref_cache(&ref_cache);
 
 cleanup:
+	transaction->state = ret ? REF_TRANSACTION_ERROR
+		: REF_TRANSACTION_CLOSED;
+
 	for (i = 0; i < n; i++)
 		if (updates[i]->lock)
 			unlock_ref(updates[i]->lock);
-- 
2.0.0.rc3.474.g3833130