Merge branch 'sp/dircache'

Merge branch 'sp/dircache'

* sp/dircache: (26 commits)
  Rewrite AssumeUnchangedOperation to use DirCache
  Rewrite UntrackOperation to use DirCacheBuilder
  Teach GitMoveDeleteHook how to move a folder recursively
  Rewrite GitMoveDeleteHook to use DirCacheBuilder
  Add a basic command line implementation of rm
  Add debugging commands to interact with the new DirCache code
  Allow the new DirCacheIterator in command line arguments
  Add JUnit tests for DirCache compatibility with C Git
  Add JUnit tests for new DirCache API
  Support copying meta fields from one DirCacheEntry to another
  Support recursively getting all entries under a subtree path
  Support a simplified model of editing index entries
  Support creating a new DirCacheEntry for an arbitrary path
  Support iterating and building a DirCache at the same time
  Support recreating a .git/index through DirCache
  Support using a DirCache within a TreeWalk
  Support the 'TREE' extension in .git/index through DirCache
  Support writing a .git/index through DirCache
  Support locking (and unlocking) a .git/index through DirCache
  Export the new DirCache API to Eclipse plugins using jgit
  ...