* RefDirectory: Add in-process fair lock for atomic updates

* RefDirectory: Retry acquiring ref locks with backoff

* Fix committing empty commits

* Support overriding a batch's reflog on a per-ReceiveCommand basis

* BatchRefUpdate: Expand javadocs and add @Nullable
* PackedBatchRefUpdate: Write reflogs
* Extract constants for reflog entry message prefixes

* Add commit check for head references

* Add connectivity check from references

* Add dfs fsck implementation

* Improve BatchRefUpdateTest readability
* Move BatchRefUpdate tests to a new file
* Implement atomic BatchRefUpdates for RefDirectory
* Separate RefUpdate.Result.REJECTED_{MISSING_OBJECT,OTHER_REASON}

* Add missing newlines at ends of Java files

* Temporarily @Ignore flaky CommitCommandTest methods

* Fix matching ignores and attributes pattern of form a/b/**.

* Add tests for updating single refs to missing objects
* Fix deleting symrefs
* RefDirectory: Throw exception if CAS of packed ref list fails
* ReceiveCommand: Explicitly check constructor preconditions
* BatchRefUpdate: Document when getPushOptions is null

* Make 'inCoreLimit' of LocalFile used in ResolveMerger configurable

* dfs: optionally store blockSize in DfsPackDescription

* dfs: silence resource warnings in DfsBlockCacheTest

* dfs: Fix DataFormatException: 0 bytes to inflate
* dfs: actually allow current DfsBlock to GC
* dfs: test for repositories sharing blocks in DfsBlockCache

* dfs: only create DfsPackFile if description has PACK

* dfs: Fix incorrect use of reference == for DfsStreamKey

* dfs: Fix build break caused by DfsStreamKey.of signature change

* dfs: Fix default DfsStreamKey to include DfsRepositoryDescription
* dfs: Shrink DfsPackDescription.sizeMap storage

* dfs: Fix caching of index, bitmap index, reverse index
* dfs: Use special ForReverseIndex DfsStreamKey wrapper instead of derive

* Derive DfsStreamKey from DfsPackDescription
* Extract BlockBasedFile base class for DfsPackFile
* Use separate DfsStreamKey for PackIndex
* Rename DfsPackKey to DfsStreamKey

* Add missing @since 4.9 for new API PackParser.setExpectedObjectCount()

* RefList: Support capacity <= 0 on new builders
* Short-circuit writing packed-refs if no refs were packed
* BatchRefUpdate: Clarify some ref prefix calls

* Make possible to overwrite the object count

* Support -merge attribute in binary macro

* Use read ahead during copyPackThroughCache

* Add a test for parsing fsck config options and expose FsckMode enum

* Add --match option for `jgit describe` to CLI
* Fix bug in multiple tag handling on DescribeCommand

* Support --match functionality in DescribeCommand

* Allow to programmatically set FastForwardMode for PullCommand

* Add support for config "pull.ff

* Fetch/PullCommand: Improve Javadoc of setRecurseSubmodules

* Improve javadoc for MergeCommand.setFastForward()

* Add tests for SubmoduleConfig

* Merge branch 'stable-4.8'

* Add a new singlePack option to PackConfig

* Prepare 4.8.1-SNAPSHOT builds

* JGit v4.8.0.201706111038-r

* Merge branch 'stable-4.8'

* Use a dedicated executor to run auto-gc in command line interface
* Allow to use an external ExecutorService for background auto-gc

* Fetch: Add --recurse-submodules and --no-recurse-submodules options

* Fix capitalization of command help summaries

* Merge branch 'stable-4.8'

* SubmoduleUpdateCommand#setCallback should return 'this'

* CloneCommand#setCallback should return 'this'

* Defer object collision check until pack stream is done

* Merge branch 'stable-4.7' into stable-4.8

* Prepare 4.7.2-SNAPSHOT builds