Merge branch 'stable-6.3' into stable-6.4

Merge branch 'stable-6.3' into stable-6.4

* stable-6.3:
  Shortcut during git fetch for avoiding looping through all local refs
  FetchCommand: fix fetchSubmodules to work on a Ref to a blob
  Silence API warnings introduced by I466dcde6
  Allow the exclusions of refs prefixes from bitmap
  PackWriterBitmapPreparer: do not include annotated tags in bitmap
  BatchingProgressMonitor: avoid int overflow when computing percentage
  Speedup GC listing objects referenced from reflogs
  FileSnapshotTest: Add more MISSING_FILE coverage

Change-Id: Iefcf5d832bd0087c1027876f2200689e1150abce