* stable-6.1:
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: Iff2fba026b49463016015b2fae1a42cf76ee2dbb