Re: Git has two ways to count modified lines

["René Scharfe" <l.s.r@web.de>]

Am 04.04.22 um 00:37 schrieb Junio C Hamano:
> René Scharfe <l.s.r@web.de> writes:
>
>> Git stores the file contents before and after your change.  It doesn't
>> store any diff, but calculates them as needed, e.g. for the commit
>> confirmation message, or when you run git diff.  So in that sense there
>> is no "the diff".  The difference between two stored states can be
>> represented in many ways.
>
> That's the crucial point to answer this question.  Even without
> break/rewrite transformation, depending on the choice of the diff
> algorithm, the same change may be shown as different patch (with
> different line count, obviously).
>
>> But I have a question to the list as well: Why is break_opt (the
>> diff_options member for --break-rewrites) enabled for git commit by
>> default?
>
> If it is, that is a bug, I would say.  Don't we initialize the
> member to "-1" at around diff.c:4580 though?

Yes, but it's set to 0 in print_commit_summary() at sequencer.c:1330.
That line was introduced by 3eb2a15eb3 (builtin-commit: make summary
output consistent with status, 2007-12-16).

--- >8 ----
Subject: [PATCH] commit, sequencer: turn off break_opt for commit summary

dc6b1d92ca (wt-status: use settings from git_diff_ui_config, 2018-05-04)
disabled diffopt.break_opt for diffstats shown by git status and in
commit templates.  For git status there isn't even a way to enable it.
Make the commit summary (shown after the commit) consistent by disabling
it there as well.

Reported-by: Laurent Lyaudet <laurent.lyaudet@gmail.com>
Signed-off-by: René Scharfe <l.s.r@web.de>
---
 sequencer.c               |  1 -
 t/t7524-commit-summary.sh | 31 +++++++++++++++++++++++++++++++
 2 files changed, 31 insertions(+), 1 deletion(-)
 create mode 100755 t/t7524-commit-summary.sh

diff --git a/sequencer.c b/sequencer.c
index a1bb39383d..85a17d45bd 100644
--- a/sequencer.c
+++ b/sequencer.c
@@ -1327,7 +1327,6 @@ void print_commit_summary(struct repository *r,
 	get_commit_format(format.buf, &rev);
 	rev.always_show_header = 0;
 	rev.diffopt.detect_rename = DIFF_DETECT_RENAME;
-	rev.diffopt.break_opt = 0;
 	diff_setup_done(&rev.diffopt);

 	refs = get_main_ref_store(the_repository);
diff --git a/t/t7524-commit-summary.sh b/t/t7524-commit-summary.sh
new file mode 100755
index 0000000000..47b2f1dc22
--- /dev/null
+++ b/t/t7524-commit-summary.sh
@@ -0,0 +1,31 @@
+#!/bin/sh
+
+test_description='git commit summary'
+. ./test-lib.sh
+
+test_expect_success 'setup' '
+	test_seq 101 200 >file &&
+	git add file &&
+	git commit -m initial &&
+	git tag initial
+'
+
+test_expect_success 'commit summary ignores rewrites' '
+	git reset --hard initial &&
+	test_seq 200 300 >file &&
+
+	git diff --stat >diffstat &&
+	git diff --stat --break-rewrites >diffstatrewrite &&
+
+	# make sure this scenario is a detectable rewrite
+	! test_cmp_bin diffstat diffstatrewrite &&
+
+	git add file &&
+	git commit -m second >actual &&
+
+	grep "1 file" <actual >actual.total &&
+	grep "1 file" <diffstat >diffstat.total &&
+	test_cmp diffstat.total actual.total
+'
+
+test_done
--
2.35.1