Release Notes: 0.4.0rc

What's new since 0.4.0b3?

• Updated git to 2.10.2 for cinnabar-helper.
• Added a new git cinnabar download command to download a helper on platforms where one is available.
• Fixed some corner cases with pack windows in the helper. This prevented cloning mozilla-central with the helper.
• Fixed bundle2 support that broke cloning from a mercurial 4.0 server in some cases.
• Fixed some corner cases involving empty files. This prevented cloning Mozilla's stylo incubator repository.
• Fixed some correctness issues in file parenting when pushing changesets pulled from one mercurial repository to another.
• Various improvements to the rules to build the helper.
• Experimental (and slow) support for pushing merges, with caveats. See issue #20 for details about the current status.