Upgrade JGit to v5.6.1.202002131546-r
Upgrade JGit to v5.6.1.202002131546-r

1b44f0e4a - JGit v5.6.1.202002131546-r
753fbaf11 - Simplify ReftableCompactor
5fd922dfd - Bump required Bazel version to 2.1.0
34c4ffff2 - Upgrade bazlets to the latest master revision
34cf825ba - Change the wildcard import to explicit ones.

Change-Id: I5b6f47a49c422210c5cf459162d078856088f183

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