[PATCH v14 15/40] refs.c: make ref_transaction_begin take an err argument

[Ronnie Sahlberg <sahlberg@google.com>]

Add an err argument to _begin so that on non-fatal failures in future ref
backends we can report a nice error back to the caller.
While _begin can currently never fail for other reasons than OOM, in which
case we die() anyway, we may add other types of backends in the future.
For example, a hypothetical MySQL backend could fail in _being with
"Can not connect to MySQL server. No route to host".

Reviewed-by: Jonathan Nieder <jrnieder@gmail.com>
Signed-off-by: Ronnie Sahlberg <sahlberg@google.com>
---
 builtin/update-ref.c | 2 +-
 refs.c               | 2 +-
 refs.h               | 2 +-
 3 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/builtin/update-ref.c b/builtin/update-ref.c
index 7c9c248..c6ad0be 100644
--- a/builtin/update-ref.c
+++ b/builtin/update-ref.c
@@ -365,7 +365,7 @@ int cmd_update_ref(int argc, const char **argv, const char *prefix)
 		die("Refusing to perform update with empty message.");
 
 	if (read_stdin) {
-		transaction = ref_transaction_begin();
+		transaction = ref_transaction_begin(&err);
 		if (delete || no_deref || argc > 0)
 			usage_with_options(git_update_ref_usage, options);
 		if (end_null)
diff --git a/refs.c b/refs.c
index d9b99c7..ee87eda 100644
--- a/refs.c
+++ b/refs.c
@@ -3387,7 +3387,7 @@ struct ref_transaction {
 	size_t nr;
 };
 
-struct ref_transaction *ref_transaction_begin(void)
+struct ref_transaction *ref_transaction_begin(struct strbuf *err)
 {
 	return xcalloc(1, sizeof(struct ref_transaction));
 }
diff --git a/refs.h b/refs.h
index 58ba365..743358f 100644
--- a/refs.h
+++ b/refs.h
@@ -257,7 +257,7 @@ enum action_on_err {
  * Begin a reference transaction.  The reference transaction must
  * be freed by calling ref_transaction_free().
  */
-struct ref_transaction *ref_transaction_begin(void);
+struct ref_transaction *ref_transaction_begin(struct strbuf *err);
 
 /*
  * The following functions add a reference check or update to a
-- 
2.0.0.582.ge25c160