Upgrade JGit to v5.6.0.201912101111-r
Upgrade JGit to v5.6.0.201912101111-r

9710c6292 - JGit v5.6.0.201912101111-r
23125abc2 - Add ability to redirect stderr from git hooks
d1bdfcd0a - Add possibility to get pure stderr output from AbortedByHookException
02dc0ca68 - Cleanup CommitAndLogCommandTest
5bf226d50 - CLI: Add support for excluding paths from Git log command
b24ec8f71 - ReftableTest: Clean up boxing warnings on usage of String.format
62d16a914 - MergedReftable: Remove unnecessary semicolon
5185d288c - Introduce RefDatabase#hasFastTipsWithSha1
3198df186 - Update Orbit to R20191126223242 for 2019-12
473527e42 - Prepare 5.6.0-SNAPSHOT builds

Change-Id: I554cee335ced3946f53e436e03936c6ad74fce4b

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