Teach --dirstat not to completely ignore rearranged lines within a file

Currently, the --dirstat analysis ignores when lines within a file are
rearranged, because the "damage" calculated by show_dirstat() is 0.
However, if the object name has changed, we already know that there is
some damage, and it is unintuitive to claim there is _no_ damage.

Teach show_dirstat() to assign a minimum amount of damage (== 1) to
entries for which the analysis otherwise yields zero damage, to still
represent that these files are changed, instead of saying that there
is no change.

Also, skip --dirstat analysis when the object names are the same (e.g. for
a pure file rename).

Signed-off-by: Johan Herland <johan@herland.net>
Acked-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 2 insertions, 2 deletions

diff --git a/Documentation/diff-options.txt b/Documentation/diff-options.txt
index 23772d6..7e4bd42 100644
--- a/Documentation/diff-options.txt
+++ b/Documentation/diff-options.txt
@@ -74,8 +74,8 @@ endif::git-format-patch[]
 	counted for the parent directory, unless `--cumulative` is used.
 +
 Note that the `--dirstat` option computes the changes while ignoring
-pure code movements within a file.  In other words, rearranging lines
-in a file is not counted as a change.
+the amount of pure code movements within a file.  In other words,
+rearranging lines in a file is not counted as much as other changes.
 
 --dirstat-by-file[=<limit>]::
 	Same as `--dirstat`, but counts changed files instead of lines.