0.6.0 release candidate 2

What's new since 0.6.0rc1?

• Improvements and bug fixes to git cinnabar self-update. Note: to upgrade
  from 0.6.0rc1, don't use the self-update command except on Windows. Please
  use the download.py script instead, or install from the release artifacts
  on https://github.com/glandium/git-cinnabar/releases/tag/0.6.0rc2.
• Disabled inexact copy/rename detection, that was enabled by accident.
• Removed dependencies on msys DLLs on Windows.
• Based on git 2.38.1.
• Other minor fixes.