refs.c: change ref_transaction_create to do error checking and return status
Do basic error checking in ref_transaction_create() and make it return
non-zero on error. Update all callers to check the result of
ref_transaction_create(). There are currently no conditions in _create that
will return error but there will be in the future. Add an err argument that
will be updated on failure.
Signed-off-by: Ronnie Sahlberg <sahlberg@google.com>
Reviewed-by: Michael Haggerty <mhagger@alum.mit.edu>
Signed-off-by: Jonathan Nieder <jrnieder@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
diff --git a/refs.h b/refs.h
index c5376ce..b648819 100644
--- a/refs.h
+++ b/refs.h
@@ -10,6 +10,38 @@
int force_write;
};
+/*
+ * A ref_transaction represents a collection of ref updates
+ * that should succeed or fail together.
+ *
+ * Calling sequence
+ * ----------------
+ * - Allocate and initialize a `struct ref_transaction` by calling
+ * `ref_transaction_begin()`.
+ *
+ * - List intended ref updates by calling functions like
+ * `ref_transaction_update()` and `ref_transaction_create()`.
+ *
+ * - Call `ref_transaction_commit()` to execute the transaction.
+ * If this succeeds, the ref updates will have taken place and
+ * the transaction cannot be rolled back.
+ *
+ * - At any time call `ref_transaction_free()` to discard the
+ * transaction and free associated resources. In particular,
+ * this rolls back the transaction if it has not been
+ * successfully committed.
+ *
+ * Error handling
+ * --------------
+ *
+ * On error, transaction functions append a message about what
+ * went wrong to the 'err' argument. The message mentions what
+ * ref was being updated (if any) when the error occurred so it
+ * can be passed to 'die' or 'error' as-is.
+ *
+ * The message is appended to err without first clearing err.
+ * err will not be '\n' terminated.
+ */
struct ref_transaction;
/*
@@ -248,7 +280,7 @@
* it must not have existed beforehand.
* Function returns 0 on success and non-zero on failure. A failure to update
* means that the transaction as a whole has failed and will need to be
- * rolled back. On failure the err buffer will be updated.
+ * rolled back.
*/
int ref_transaction_update(struct ref_transaction *transaction,
const char *refname,
@@ -262,11 +294,15 @@
* that the reference should have after the update; it must not be the
* null SHA-1. It is verified that the reference does not exist
* already.
+ * Function returns 0 on success and non-zero on failure. A failure to create
+ * means that the transaction as a whole has failed and will need to be
+ * rolled back.
*/
-void ref_transaction_create(struct ref_transaction *transaction,
- const char *refname,
- const unsigned char *new_sha1,
- int flags);
+int ref_transaction_create(struct ref_transaction *transaction,
+ const char *refname,
+ const unsigned char *new_sha1,
+ int flags,
+ struct strbuf *err);
/*
* Add a reference deletion to transaction. If have_old is true, then
@@ -282,8 +318,6 @@
* Commit all of the changes that have been queued in transaction, as
* atomically as possible. Return a nonzero value if there is a
* problem.
- * If err is non-NULL we will add an error string to it to explain why
- * the transaction failed. The string does not end in newline.
*/
int ref_transaction_commit(struct ref_transaction *transaction,
const char *msg, struct strbuf *err);
