shortlog: de-duplicate trailer values

The current documentation is vague about what happens with
--group=trailer:signed-off-by when we see a commit with:

  Signed-off-by: One
  Signed-off-by: Two
  Signed-off-by: One

We clearly should credit both "One" and "Two", but should "One" get
credited twice? The current code does so, but mostly because that was
the easiest thing to do. It's probably more useful to count each commit
at most once. This will become especially important when we allow
values from multiple sources in a future patch.

Signed-off-by: Jeff King <peff@peff.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 28 insertions, 0 deletions

diff --git a/t/t4201-shortlog.sh b/t/t4201-shortlog.sh
index e97d891..83dbbc4 100755
--- a/t/t4201-shortlog.sh
+++ b/t/t4201-shortlog.sh
@@ -234,4 +234,32 @@ test_expect_success 'shortlog --group=trailer:signed-off-by' '
 	test_cmp expect actual
 '
 
+test_expect_success 'shortlog de-duplicates trailers in a single commit' '
+	git commit --allow-empty -F - <<-\EOF &&
+	subject one
+
+	this message has two distinct values, plus a repeat
+
+	Repeated-trailer: Foo
+	Repeated-trailer: Bar
+	Repeated-trailer: Foo
+	EOF
+
+	git commit --allow-empty -F - <<-\EOF &&
+	subject two
+
+	similar to the previous, but without the second distinct value
+
+	Repeated-trailer: Foo
+	Repeated-trailer: Foo
+	EOF
+
+	cat >expect <<-\EOF &&
+	     2	Foo
+	     1	Bar
+	EOF
+	git shortlog -ns --group=trailer:repeated-trailer -2 HEAD >actual &&
+	test_cmp expect actual
+'
+
 test_done