* master:
Fixed since tags added for new merge constants
Add filtering with help of DirCacheCheckout.getContent()
Avoid warning "no explicit project encoding"
Add mergetool merge feature (execute external tool)
Add command line support for "git mergetool"
Add config reader for user-defined mergetools
Add difftool compare feature (execute external tool)
Change-Id: Ie215b8205b85cfd9efddb622c90dfad7a5ae0caa