* Clarify operator precedence to fix errorprone error

* dfs: handle short copies

* pgm: Fix missing braces in Push.run()
* pgm: Handle exceptions in Push command
* pgm: Fix missing braces in MergeBase.run()
* pgm: Handle IOException in MergeBase command
* pgm: Fix missing braces in Merge command
* pgm: Handle exceptions in Merge command
* pgm: Fix missing braces in LsTree.run()
* pgm: Handle exceptions in LsTree command
* pgm: Fix missing braces in LsRemote.run()
* pgm: Handle exceptions in LsRemote command
* pgm: Handle exceptions in LsFiles command
* pgm: Fix missing braces in Log.run()
* pgm: Handle exceptions in Log command
* pgm: Handle exceptions in Init command
* pgm: Handle IOException in IndexPack command
* pgm: Fix missing braces in Fetch.run()
* pgm: Handle IOException in Fetch command
* pgm: Handle GitAPIException in Gc command
* pgm: Fix missing braces in DiffTree.run()
* pgm: Handle exceptions in DiffTree command

* Add --ssh option to command-line commands

* Upgrade spotbugs-maven-plugin to 3.1.0
* Add header Automatic-Module-Name for Java 9
* Merge branch 'stable-4.9'

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

* dfs: silence resource warnings in DfsBlockCacheTest

* GC.prune(Set<ObjectId>): return early if objects directory is empty

* ReceivePack: report protocol parsing failures on channel 3
* ReceivePack: catch InvalidObjectIdException while parsing shallow
* ReceivePack: remove unnecessary try-catch around parseCommand
* ReceivePack: enable capabilities immediately on first line

* Prune UNREACHABLE_GARBAGE packs when they expire
* Use try-with-resources in DfsGarbageCollector.writePack
* Fix lastModified to be consistent in DfsGarbageCollector
* Add GC_REST PackSource to better order DFS packs

* ResetCommandTest: Use Git member in testHardResetAfterSquashMerge

* submodule test: Use config.unset instead of setting to null

* Allow configuration of receive pack's ObjectChecker through fsck.*
* Correct fetch to use fetch.fsckObjects and transfer.fsckObjects
* Default receive.fsckObjects to transfer.fsckObjects
* Allow ReceivePack callers to configure their own ObjectChecker
* Check for duplicate names after folding case in ObjectChecker
* Change DirCacheCheckout to verify path using ObjectChecker
* Reject mixed case .git on Mac OS in ObjectChecker
* Reject special Windows device names in ObjectChecker
* Allow an ObjectChecker to reject special characters for Windows
* Reject '.git' as a tree name in ObjectChecker
* Extract path segment check function in ObjectChecker
* Permit ObjectChecker to optionally accept leading '0' in trees

* Load .gitmodules config before adding values to it

* Do not use the deprecated Tree class internally

* PackWriter: support excluding objects already in other packs