Merge branch 'stable-6.6' into stable-6.7

* stable-6.6:
  PackConfig: fix @since tags
  Remove unused API problem filters
  Add support for git config repack.packKeptObjects
  Do not exclude objects in locked packs from bitmap processing

Change-Id: I29241619e6c09933bb856e486f379be10dd609c2

diff --cc Documentation/config-options.md
Simple merge

diff --cc org.eclipse.jgit/src/org/eclipse/jgit/api/GarbageCollectCommand.java
Simple merge

diff --cc org.eclipse.jgit/src/org/eclipse/jgit/internal/storage/file/GC.java
Simple merge

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

diff --cc org.eclipse.jgit/src/org/eclipse/jgit/storage/pack/PackConfig.java
Simple merge