Merge branch 'pt/pull-tests'

Add more test coverage to "git pull".

* pt/pull-tests:
  t5520: check reflog action in fast-forward merge
  t5521: test --dry-run does not make any changes
  t5520: test --rebase failure on unborn branch with index
  t5520: test --rebase with multiple branches
  t5520: test work tree fast-forward when fetch updates head
  t5520: test for failure if index has unresolved entries
  t5520: test no merge candidates cases
  t5520: prevent field splitting in content comparisons