Support cancellation in push operation

This commit adds cancellation for the push operation. This work consists of:

1) Support cancellation during push operation
    - During object counting phase
    - During network transfer phase
        - Propagate GIT_EUSER error code out to caller
2) Improve cancellation support during fetch
    - Handle cancellation request during network transfer phase
    - Clear error string when cancelled during indexing
3) Fix error handling in git_smart__download_pack

Cancellation during push is still only handled in the pack building and
network transfer stages of push (and not during packbuilding).

1 files changed, 1 insertions, 3 deletions

diff --git a/src/push.c b/src/push.c
index 698079253..a799db8d0 100644
--- a/src/push.c
+++ b/src/push.c
@@ -582,7 +582,7 @@ static int calculate_work(git_push *push)
 
 static int do_push(git_push *push)
 {
-	int error;
+	int error = 0;
 	git_transport *transport = push->remote->transport;
 
 	if (!transport->push) {
@@ -611,8 +611,6 @@ static int do_push(git_push *push)
 		(error = transport->push(transport, push)) < 0)
 		goto on_error;
 
-	error = 0;
-
 on_error:
 	git_packbuilder_free(push->pb);
 	return error;