* Merge branch 'stable-5.12'

* Update orbit to S20210406213021 and add 4.20-staging target

* IO: fix IO.readFully(InputStream, byte[], int)
* LFS: make pointer parsing more robust

* [pgm] add option --timeout to clone command

* Suppress API error for new method BitmapIndex.Bitmap#retrieveCompressed
* Fix wrong @since tags added in dcb0265

* PackBitmapIndex: Set distance threshold
* PackBitmapIndex: Not buffer inflated bitmap in BasePackBitmapIndex
* PackBitmapIndex: Remove convertedBitmaps in the Remapper
* PackBitmapIndex: Reduce memory usage in GC
* PackBitmapIndex: Add AddToBitmapWithCacheFilter class
* PackBitmapIndex: Add util methods and builder to BitmapCommit
* PackBitmapIndex: Move BitmapCommit to a top-level class
* Refactor: Make retriveCompressed an method of the Bitmap class

* Bump Bazel version to 3.1.0

* TreeRevFilterTest: Simplify filter used

* ProtocolV2Parser: Introduce advertise sideband-all option

* UploadPack: move writing of "packfile" header

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

* RawParseUtils: Avoid import of java.nio.charset.StandardCharsets
* Consistently import constants from StandardCharsets as static
* LocalDiskRepositoryTestCase#createRepository: Default auto-close to false
* UploadPack: Suppress false-positive resource leak warning

* Implement signing commits using BouncyCastle
* Add signing options to commit CLI
* Allow CommitCommand to sign commits

* Update Eclipse Java compiler
* Update Jetty to 9.4.14

* Bazel: Automatically format build file with buildifier 0.20.0

* Fix test setup for Eclipse Photon and greater
* Update JGit target platforms to Orbit I20181102163257

* CLIText: Fix typo: remotes's -> remote's
* CLIText: Fix typo: 'amd' -> 'and'

* Configure classpath for separate test sources in Eclipse
* Disable Eclipse warning about unrecognized @SuppressWarnings value

* AbbreviationTest: Open FileOutputStream in try-with-resource

* gc: Add options to preserve and prune old pack files

* Fix non-escaped quotes in JGitText.properties

* Delete deprecated TemporaryBuffer.LocalFile constructors
* Delete deprecated FileUtils.setExecute(File, boolean)
* Delete deprecated WorkingTreeIterator.isModified(DirCacheEntry, boolean)
* Delete deprecated UploadPackMayNotContinueException
* Delete deprecated TransferConfig.isFsckObjects()
* Delete deprecated TextBuiltin.out
* Delete deprecated Merger.getBaseCommit()

* Expose ReceiveCommand version of TrackingRefUpdate

* Add isRebasing to RepositoryState

* Do not attempt to read bitmap from invalid pack
* Rename DfsPackFile getBitmap method to match PackFile

* Update last release version to 2.3.1.201302201838-r

* Accept '-' instead of space in enum config values

* Only increment mod count if packed-refs file changes

* Exclude org.eclipse.jgit from pack200 packing