* Merge branch 'stable-5.9'

* UploadPack: Use more relevant refs first in object reachability check
* UploadPack: Refactor to generalize the object reachability checks
* UploadPack: Use BitmappedReachabilityChecker for not advertised wants
* revwalk: Introduce bitmap-based object reachability checker
* revwalk: Extract ObjectReachabilityChecker interface
* UploadPack: Extract walk-based reachability check

* RequestValidatorTestCase: Tests for the request validators
* UploadPackTest: Move "reachability" tests to its own file

* Include filekey file attribute when comparing FileSnapshots
* Measure file timestamp resolution used in FileSnapshot
* Fix FileSnapshot's consideration of file size

* LfsGson: Remove unnecessary @since tag

* Prepare 5.1.3-SNAPSHOT builds

* Fix a GC scalability issue when selecting commit bitmaps
* Test uniform bitmap commit selection across multiple branches

* LargePackedWholeObject#openStream: Suppress resource warning

* FS: Open TemporaryBuffer in try-with-resource
* EditListTest: Open InputStream in try-with-resource
* EGitPatchHistoryTest: Open BufferedReader in try-with-resource
* T0003_BasicTest: Use CommitBuilder.setEncoding(Charset)
* WalkEncryptionTest: Use StandardCharsets.UTF_8
* GetTextTest: Use StandardCharsets constants instead of CharSet.forName
* EGitPatchHistoryTest: Set input stream encoding with constant
* DirCacheIterator: Open InputStream in try-with-resource
* DumbClientSmartServerTest: Open auto-closeable resources in try-with-resource
* DirCacheCheckoutTest: Open FileInputStream in try-with-resource
* DiffFormatterReflowTest: Open InputStream in try-with-resource

* AdvertiseErrorTest: Open Transport in try-with-resource
* AddCommandTest: Open PrintWriter in try-with-resource
* FileBasedConfigTest: Open FileOutputStream in try-with-resource
* WalkRemoteObjectDatabase: Open auto-closeable resources in try-with-resource
* TransportSftp: Open BufferedReader in try-with-resource
* ReflogReaderTest: Open FileOutputStream in try-with-resource
* ReflogReaderTest: Fix indentation
* ReflogWriterTest: Open FileInputStream in try-with-resource
* TransportHttp: Open auto-closeable resources in try-with-resource
* RebaseCommandTest: Open BufferedReader in try-with-resource
* DirCacheCGitCompatabilityTest: Open BufferedReader in try-with-resource
* LockFile: Open FileInputStream in try-with-resource
* CheckoutCommandTest: Open FileInputStream in try-with-resource
* SmudgeFilter: Fix Integer boxing warning
* Add ConfigConstants.CONFIG_SECTION_LFS

* Fix HttpClientConnection leaking temporary buffer files

* JGit v4.2.0.201601211800-r

* Prepare 4.2.0-SNAPSHOT builds

* Annotated to be removed Tree API with @noreference and @noextend

* Fixed javadoc: the getBranch() and getFullBranch() can return null

* Allow full compiles on Java 8.

* Disable response compression on /git-receive-pack URLs

* Add config constant for "mergeoptions"

* Make an exception for the formatting rules (turn off) for some files

* Get rid of warnings about empty statments
* Removed unused parameters from private methods
* cleanup: Remove unused declarations
* Make FS OS X detection work for OpenJDK

* UnsupportedCredentialItem with password authentication

* Refactor ResolveMerger

* Cleanup curly braces