[PATCHv2 0/3] --dirstat fixes

Here's a reroll of the previous series. Changes since v1:

- Adopt Junio's phrasing of the differences between --dirstat and
  regular diff (--stat)

- Detect and ignore pure renames in the diff queue. This is done by
  comparing the SHA1s of each file pair, and if they are equal, we
  know the files are identical, and should not show up in --dirstat.

  As an extra bonus in this version, when the SHA1s do match, we can
  bypass the usual --dirstat analysis, because we know it would find
  no changes. Instead, we can directly set damage = 0 in that case.

I've looked at the contents of the diff queue and resulting output in a variety of cases:

- files with no changes, rearranged lines, and other changes
- files that are copied, moved, or not moved
- unstaged changes, staged changes, committed changes
- diff options: (none), --stat, --dirstat, and --dirstat-by-file
- diff options: (none), -M, and -C -C

(324 variations in total) and I'm fairly sure about the current patches and how they interact with the diff queue.

A remaining question AFAICS is if there's a different (i.e. better) way to (cheaply) estimate the damage contributed by code movements within a file. The current "damage = 1" approach is somewhat crude, but IMHO still better that ignoring code movements altogether.

Have fun! :)

...Johan

Johan Herland (3):
  --dirstat: Describe non-obvious differences relative to --stat or regular diff
  --dirstat-by-file: Make it faster and more correct
  Teach --dirstat to not completely ignore rearranged lines within a file

 Documentation/diff-options.txt                     |    4 ++
 diff.c                                             |   40 ++++++++++++++++++--
 t/t4013-diff-various.sh                            |   27 ++++++++++---
 .../diff.diff_--dirstat-by-file_initial_rearrange  |    3 +
 t/t4013/diff.diff_--dirstat_initial_rearrange      |    3 +
 ...tch_--stdout_--cover-letter_-n_initial..master^ |    2 +-
 t/t4013/diff.log_--decorate=full_--all             |    6 +++
 t/t4013/diff.log_--decorate_--all                  |    6 +++
 8 files changed, 80 insertions(+), 11 deletions(-)
 create mode 100644 t/t4013/diff.diff_--dirstat-by-file_initial_rearrange
 create mode 100644 t/t4013/diff.diff_--dirstat_initial_rearrange