Merge branch 'stable-6.1' into stable-6.2

* stable-6.1:
  [benchmarks] Remove profiler configuration
  Add SHA1 benchmark
  [benchmarks] Set version of maven-compiler-plugin to 3.8.1
  Fix running JMH benchmarks
  Add option to allow using JDK's SHA1 implementation
  Ignore IllegalStateException if JVM is already shutting down

Change-Id: Ie433c46a01a0f33848d54ecf99b30a44ca01e286

diff --cc org.eclipse.jgit.benchmarks/pom.xml
Simple merge

diff --cc org.eclipse.jgit/src/org/eclipse/jgit/lib/ConfigConstants.java
Simple merge