[PATCH v3 0/9] diffcore-rename improvements

This patch series includes 3 small code cleanups, 1 small bug fix (or perhaps just a UI improvement -- it's a very minor issue either way), more testcases, and 3 performance improvements. The first 7 patches are relatively easy to review, while the second to last one...is a bit more involved (but provided the biggest performance boost).

Changes since v2:

 * Fixed spelling error: remove unnecessary double c in 'unneccessary'
   (thanks to Christian for spotting)

Elijah Newren (9):
  diffcore-rename: rename num_create to num_destinations
  diffcore-rename: avoid usage of global in too_many_rename_candidates()
  diffcore-rename: simplify limit check
  diffcore-rename: reduce jumpiness in progress counters
  t4058: add more tests and documentation for duplicate tree entry
    handling
  t4058: explore duplicate tree entry handling in a bit more detail
  diffcore-rename: simplify and accelerate register_rename_src()
  diffcore-rename: accelerate rename_dst setup
  diffcore-rename: remove unnecessary duplicate entry checks

 diffcore-rename.c          | 209 ++++++++++++++-----------------------
 t/t4058-diff-duplicates.sh | 114 +++++++++++++++++++-
 2 files changed, 192 insertions(+), 131 deletions(-)

base-commit: 3a0b884caba2752da0af626fb2de7d597c844e8b
Published-As: https://github.com/gitgitgadget/git/releases/tag/pr-git-929%2Fnewren%2Fdiffcore-rename-improvements-v3
Fetch-It-Via: git fetch https://github.com/gitgitgadget/git pr-git-929/newren/diffcore-rename-improvements-v3
Pull-Request: https://github.com/git/git/pull/929

Range-diff vs v2:

  1:  428d8204894 =  1:  428d8204894 diffcore-rename: rename num_create to num_destinations
  2:  fc62f4c4f89 =  2:  fc62f4c4f89 diffcore-rename: avoid usage of global in too_many_rename_candidates()
  3:  7214fa73fdd =  3:  7214fa73fdd diffcore-rename: simplify limit check
  4:  bf3581b1ac1 =  4:  bf3581b1ac1 diffcore-rename: reduce jumpiness in progress counters
  5:  9a4a3159acf =  5:  9a4a3159acf t4058: add more tests and documentation for duplicate tree entry handling
  6:  8db27892c59 =  6:  8db27892c59 t4058: explore duplicate tree entry handling in a bit more detail
  7:  a58639b2927 =  7:  a58639b2927 diffcore-rename: simplify and accelerate register_rename_src()
  8:  85714e1583d =  8:  85714e1583d diffcore-rename: accelerate rename_dst setup
  9:  af256b1c534 !  9:  723b0e55e75 diffcore-rename: remove unneccessary duplicate entry checks
     @@ Metadata
      Author: Elijah Newren <newren@gmail.com>
      
       ## Commit message ##
     -    diffcore-rename: remove unneccessary duplicate entry checks
     +    diffcore-rename: remove unnecessary duplicate entry checks
      
          Commit 25d5ea410f ("[PATCH] Redo rename/copy detection logic.",
          2005-05-24) added a duplicate entry check on rename_src in order to