Merge branch 'stable-6.3' into stable-6.4

* stable-6.3:
  Use Java 11 ProcessHandle to get pid of the current process
  Acquire file lock "gc.pid" before running gc
  Silence API errors introduced by 9424052f

Change-Id: Ic40dbab18616d8d9fe3820b9890c86652b80eb47

diff --cc org.eclipse.jgit/resources/org/eclipse/jgit/internal/JGitText.properties
Simple merge

diff --cc org.eclipse.jgit/src/org/eclipse/jgit/internal/JGitText.java
Simple merge