Merge branch 'en/fill-directory-exponential' into pu

The directory traversal code had redundant recursive calls which
made its performance characteristics exponential with respect to
the depth of the tree, which was corrected.

* en/fill-directory-exponential:
  t7063: blindly accept diffs
  dir: replace exponential algorithm with a linear one
  dir: refactor treat_directory to clarify control flow
  dir: fix confusion based on variable tense
  dir: fix broken comment
  dir: consolidate treat_path() and treat_one_path()

Author: gitster