Merge branch 'sr/transport-helper-fix'

Merge branch 'sr/transport-helper-fix'

* sr/transport-helper-fix: (21 commits)
  transport-helper: die early on encountering deleted refs
  transport-helper: implement marks location as capability
  transport-helper: Use capname for refspec capability too
  transport-helper: change import semantics
  transport-helper: update ref status after push with export
  transport-helper: use the new done feature where possible
  transport-helper: check status code of finish_command
  transport-helper: factor out push_update_refs_status
  fast-export: support done feature
  fast-import: introduce 'done' command
  git-remote-testgit: fix error handling
  git-remote-testgit: only push for non-local repositories
  remote-curl: accept empty line as terminator
  remote-helpers: export GIT_DIR variable to helpers
  git_remote_helpers: push all refs during a non-local export
  transport-helper: don't feed bogus refs to export push
  git-remote-testgit: import non-HEAD refs
  t5800: document some non-functional parts of remote helpers
  t5800: use skip_all instead of prereq
  t5800: factor out some ref tests
  ...