tree 3a9b5394de7a6e04a285ef6ece10c2f6ef24af8a
parent 5b298ebe23794afcce3205925d3538e41d9afa86
author Fabio Ponciroli <ponch78@gmail.com> 1777985431 +0200
committer Fabio Ponciroli <ponch78@gmail.com> 1777985431 +0200

FetchProcess: Report lock failure when destination ref changes

Snapshot local refs before opening the fetch connection so
`TrackingRefUpdate`s use the value populated when the fetch starts as
their expected old object ID.

Before this change, local refs were loaded lazily while processing
"wants". If another process changed or created the destination ref after
the fetch started but before that lazy read, JGit used the newer local
value as the expected old object ID. The final ref update could then
succeed and overwrite the concurrent local change.

Load the local ref snapshot before the remote fetch connection is
opened. Concurrent destination ref changes now make the expected old
object ID differ from the current ref value, causing the update to
report LOCK_FAILURE instead of clobbering the newer local ref.

The tests trigger the race condition by using TestProtocol.registerProto(...)
with a custom UploadPackFactory. The factory updates the local
destination ref immediately before returning the UploadPack, which
places the concurrent local change after FetchProcess starts but
before it finishes building the TrackingRefUpdate.

Bug: jgit-252
Change-Id: Ib46363251862a7018c60bd4c36f003d267f354d5