format-patch: support deep threading

For deep threading mode, i.e., the mode that gives a thread structured
like

  + [PATCH 0/n] Cover letter
   `-+ [PATCH 1/n] First patch
      `-+ [PATCH 2/n] Second patch
         `-+ ...

we currently have to use 'git send-email --thread' (the default).  On
the other hand, format-patch also has a --thread option which gives
shallow mode, i.e.,

  + [PATCH 0/n] Cover letter
  |-+ [PATCH 1/n] First patch
  |-+ [PATCH 2/n] Second patch
  ...

To reduce the confusion resulting from having two indentically named
features in different tools giving different results, let format-patch
take an optional argument '--thread=deep' that gives the same output
as 'send-mail --thread'.  With no argument, or 'shallow', behave as
before.  Also add a configuration variable format.thread with the same
semantics.

Signed-off-by: Thomas Rast <trast@student.ethz.ch>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

1 files changed, 120 insertions, 0 deletions

diff --git a/t/t4014-format-patch.sh b/t/t4014-format-patch.sh
index 8b970c3..ebfc4a6 100755
--- a/t/t4014-format-patch.sh
+++ b/t/t4014-format-patch.sh
@@ -257,6 +257,126 @@ test_expect_success 'thread cover-letter in-reply-to' '
 		--in-reply-to="<test.message>" --thread master
 '
 
+test_expect_success 'thread explicit shallow' '
+	check_threading expect.cl-irt --cover-letter \
+		--in-reply-to="<test.message>" --thread=shallow master
+'
+
+cat > expect.deep <<EOF
+---
+Message-Id: <0>
+---
+Message-Id: <1>
+In-Reply-To: <0>
+References: <0>
+---
+Message-Id: <2>
+In-Reply-To: <1>
+References: <0>
+	<1>
+EOF
+
+test_expect_success 'thread deep' '
+	check_threading expect.deep --thread=deep master
+'
+
+cat > expect.deep-irt <<EOF
+---
+Message-Id: <0>
+In-Reply-To: <1>
+References: <1>
+---
+Message-Id: <2>
+In-Reply-To: <0>
+References: <1>
+	<0>
+---
+Message-Id: <3>
+In-Reply-To: <2>
+References: <1>
+	<0>
+	<2>
+EOF
+
+test_expect_success 'thread deep in-reply-to' '
+	check_threading expect.deep-irt  --thread=deep \
+		--in-reply-to="<test.message>" master
+'
+
+cat > expect.deep-cl <<EOF
+---
+Message-Id: <0>
+---
+Message-Id: <1>
+In-Reply-To: <0>
+References: <0>
+---
+Message-Id: <2>
+In-Reply-To: <1>
+References: <0>
+	<1>
+---
+Message-Id: <3>
+In-Reply-To: <2>
+References: <0>
+	<1>
+	<2>
+EOF
+
+test_expect_success 'thread deep cover-letter' '
+	check_threading expect.deep-cl --cover-letter --thread=deep master
+'
+
+cat > expect.deep-cl-irt <<EOF
+---
+Message-Id: <0>
+In-Reply-To: <1>
+References: <1>
+---
+Message-Id: <2>
+In-Reply-To: <0>
+References: <1>
+	<0>
+---
+Message-Id: <3>
+In-Reply-To: <2>
+References: <1>
+	<0>
+	<2>
+---
+Message-Id: <4>
+In-Reply-To: <3>
+References: <1>
+	<0>
+	<2>
+	<3>
+EOF
+
+test_expect_success 'thread deep cover-letter in-reply-to' '
+	check_threading expect.deep-cl-irt --cover-letter \
+		--in-reply-to="<test.message>" --thread=deep master
+'
+
+test_expect_success 'thread via config' '
+	git config format.thread true &&
+	check_threading expect.thread master
+'
+
+test_expect_success 'thread deep via config' '
+	git config format.thread deep &&
+	check_threading expect.deep master
+'
+
+test_expect_success 'thread config + override' '
+	git config format.thread deep &&
+	check_threading expect.thread --thread master
+'
+
+test_expect_success 'thread config + --no-thread' '
+	git config format.thread deep &&
+	check_threading expect.no-threading --no-thread master
+'
+
 test_expect_success 'excessive subject' '
 
 	rm -rf patches/ &&