[PATCH 1/3] --dirstat: Document shortcomings compared to --stat or regular diff

[Johan Herland <johan@herland.net>]

Also add a testcase documenting the current behavior.

Signed-off-by: Johan Herland <johan@herland.net>
---
 Documentation/diff-options.txt                     |    5 +++
 t/t4013-diff-various.sh                            |   27 +++++++++++++++----
 t/t4013/diff.diff_--dirstat_initial_rearrange      |    2 +
 ...tch_--stdout_--cover-letter_-n_initial..master^ |    2 +-
 t/t4013/diff.log_--decorate=full_--all             |    6 ++++
 t/t4013/diff.log_--decorate_--all                  |    6 ++++
 6 files changed, 41 insertions(+), 7 deletions(-)
 create mode 100644 t/t4013/diff.diff_--dirstat_initial_rearrange

diff --git a/Documentation/diff-options.txt b/Documentation/diff-options.txt
index c93124b..25e48c4 100644
--- a/Documentation/diff-options.txt
+++ b/Documentation/diff-options.txt
@@ -72,6 +72,11 @@ endif::git-format-patch[]
 	a cut-off percent (3% by default) are not shown. The cut-off percent
 	can be set with `--dirstat=<limit>`. Changes in a child directory are not
 	counted for the parent directory, unless `--cumulative` is used.
++
+Note that `--dirstat` does not use the regular diff machinery to calculate
+the changes (rather it is based on the rename detection machinery). Therefore,
+`--dirstat` may skip some changes that `--stat` does not skip. For example,
+rearranging the lines in a file will not be detected by `--dirstat`.
 
 --dirstat-by-file[=<limit>]::
 	Same as `--dirstat`, but counts changed files instead of lines.
diff --git a/t/t4013-diff-various.sh b/t/t4013-diff-various.sh
index 5daa0f2..8cc94ef 100755
--- a/t/t4013-diff-various.sh
+++ b/t/t4013-diff-various.sh
@@ -80,18 +80,31 @@ test_expect_success setup '
 
 	git config log.showroot false &&
 	git commit --amend &&
+
+	GIT_AUTHOR_DATE="2006-06-26 00:06:00 +0000" &&
+	GIT_COMMITTER_DATE="2006-06-26 00:06:00 +0000" &&
+	export GIT_AUTHOR_DATE GIT_COMMITTER_DATE &&
+	git checkout -b rearrange initial &&
+	for i in B A; do echo $i; done >dir/sub &&
+	git add dir/sub &&
+	git commit -m "Rearranged lines in dir/sub" &&
+	git checkout master &&
+
 	git show-branch
 '
 
 : <<\EOF
 ! [initial] Initial
  * [master] Merge branch 'side'
-  ! [side] Side
----
- -  [master] Merge branch 'side'
- *+ [side] Side
- *  [master^] Second
-+*+ [initial] Initial
+  ! [rearrange] Rearranged lines in dir/sub
+   ! [side] Side
+----
+  +  [rearrange] Rearranged lines in dir/sub
+ -   [master] Merge branch 'side'
+ * + [side] Side
+ *   [master^] Third
+ *   [master~2] Second
++*++ [initial] Initial
 EOF
 
 V=`git version | sed -e 's/^git version //' -e 's/\./\\./g'`
@@ -287,6 +300,8 @@ diff --no-index --name-status -- dir2 dir
 diff --no-index dir dir3
 diff master master^ side
 diff --dirstat master~1 master~2
+# --dirstat does NOT pick up changes that simply rearrange existing lines
+diff --dirstat initial rearrange
 EOF
 
 test_expect_success 'log -S requires an argument' '
diff --git a/t/t4013/diff.diff_--dirstat_initial_rearrange b/t/t4013/diff.diff_--dirstat_initial_rearrange
new file mode 100644
index 0000000..fb2e17d
--- /dev/null
+++ b/t/t4013/diff.diff_--dirstat_initial_rearrange
@@ -0,0 +1,2 @@
+$ git diff --dirstat initial rearrange
+$
diff --git a/t/t4013/diff.format-patch_--stdout_--cover-letter_-n_initial..master^ b/t/t4013/diff.format-patch_--stdout_--cover-letter_-n_initial..master^
index 1f0f9ad..3b4e113 100644
--- a/t/t4013/diff.format-patch_--stdout_--cover-letter_-n_initial..master^
+++ b/t/t4013/diff.format-patch_--stdout_--cover-letter_-n_initial..master^
@@ -1,7 +1,7 @@
 $ git format-patch --stdout --cover-letter -n initial..master^
 From 9a6d4949b6b76956d9d5e26f2791ec2ceff5fdc0 Mon Sep 17 00:00:00 2001
 From: C O Mitter <committer@example.com>
-Date: Mon, 26 Jun 2006 00:05:00 +0000
+Date: Mon, 26 Jun 2006 00:06:00 +0000
 Subject: [DIFFERENT_PREFIX 0/2] *** SUBJECT HERE ***
 
 *** BLURB HERE ***
diff --git a/t/t4013/diff.log_--decorate=full_--all b/t/t4013/diff.log_--decorate=full_--all
index d155e0b..44d4525 100644
--- a/t/t4013/diff.log_--decorate=full_--all
+++ b/t/t4013/diff.log_--decorate=full_--all
@@ -1,4 +1,10 @@
 $ git log --decorate=full --all
+commit cd4e72fd96faed3f0ba949dc42967430374e2290 (refs/heads/rearrange)
+Author: A U Thor <author@example.com>
+Date:   Mon Jun 26 00:06:00 2006 +0000
+
+    Rearranged lines in dir/sub
+
 commit 59d314ad6f356dd08601a4cd5e530381da3e3c64 (HEAD, refs/heads/master)
 Merge: 9a6d494 c7a2ab9
 Author: A U Thor <author@example.com>
diff --git a/t/t4013/diff.log_--decorate_--all b/t/t4013/diff.log_--decorate_--all
index fd7c3e6..27d3eab 100644
--- a/t/t4013/diff.log_--decorate_--all
+++ b/t/t4013/diff.log_--decorate_--all
@@ -1,4 +1,10 @@
 $ git log --decorate --all
+commit cd4e72fd96faed3f0ba949dc42967430374e2290 (rearrange)
+Author: A U Thor <author@example.com>
+Date:   Mon Jun 26 00:06:00 2006 +0000
+
+    Rearranged lines in dir/sub
+
 commit 59d314ad6f356dd08601a4cd5e530381da3e3c64 (HEAD, master)
 Merge: 9a6d494 c7a2ab9
 Author: A U Thor <author@example.com>
-- 
1.7.5.rc1