implement LocalQuickFix interface in addition to IntentionAction
removed dependency on lang-api
interruptibility
test dependency added
[vcs] generify a method
[git] Refactor GitRepositoryReader

* Remove the complicated PackedRefsLineResultHandler.
* Instead make parseRefsLine return a (hash, name) pair,
  and supply a nullable Condition to split cases when only the first
  match is needed, and when all values are needed.
* Avoid the substring memory issue while parsing line.
[git] Simplify packed-refs line parsing a bit.