Refactor how we handle trailers

With the addition of b4 trailers it became pretty obvious that the way
we originally implemented trailers didn't age well. This refactor does
the following:

- introduces LoreTrailer class to replace passing trailers as tuples
- reimplements trailer-order with strict adherence to chain-of-custody
  rules
- adds tests to most common trailer follow-up/ordering cases

Signed-off-by: Konstantin Ryabitsev <konstantin@linuxfoundation.org>

16 files changed, 795 insertions, 0 deletions

diff --git a/tests/samples/trailers-followup-custody-ref-ordered.txt b/tests/samples/trailers-followup-custody-ref-ordered.txt
new file mode 100644
index 0000000..383befb
--- /dev/null
+++ b/tests/samples/trailers-followup-custody-ref-ordered.txt
@@ -0,0 +1,41 @@
+From git@z Thu Jan  1 00:00:00 1970
+Subject: [PATCH] Simple test
+From: Test Test <test@example.com>
+Date: Tue, 30 Aug 2022 11:19:07 -0400
+Message-Id: <orig-message@example.com>
+To: Some List <list-1@lists.example.com>
+Cc: Dev Eloper1 <dev-eloper1@example.com>, Dev Eloper2 <dev-eloper2@example.com>
+MIME-Version: 1.0
+Content-Type: text/plain; charset="utf-8"
+Content-Transfer-Encoding: 7bit
+
+Follow-up trailer collating test.
+
+Link: https://msgid.link/some@msgid.here
+Reviewed-by: Original Reviewer <original-reviewer@example.com>
+Signed-off-by: Original Submitter <original-submitter@example.com>
+Cc: Dev Eloper1 <dev-eloper1@example.com>
+Cc: Dev Eloper2 <dev-eloper2@example.com>
+Cc: Some List <list-1@lists.example.com>
+Fixes: abcdef01234567890
+Link: https://lore.kernel.org/some@msgid.here  # bug discussion
+Suggested-by: Friendly Suggester <suggested-by@example.com>
+Reviewed-by: Followup Reviewer1 <followup-reviewer1@example.com>
+Tested-by: Followup Reviewer2 <followup-reviewer2@example.com>
+Signed-off-by: Test Override <test-override@example.com>
+---
+
+diff --git a/b4/junk.py b/b4/junk.py
+index 12345678..23456789 100644
+--- a/b4/junk.py
+--- b/b4/junk.py
+@@@ -1,1 +1,1 @@ def junk():
+ 
+ 
+-junk1
++junk2
+ 
+ 
+-- 
+2.wong.fu
+
diff --git a/tests/samples/trailers-followup-custody-ref-unordered.txt b/tests/samples/trailers-followup-custody-ref-unordered.txt
new file mode 100644
index 0000000..4b238da
--- /dev/null
+++ b/tests/samples/trailers-followup-custody-ref-unordered.txt
@@ -0,0 +1,41 @@
+From git@z Thu Jan  1 00:00:00 1970
+Subject: [PATCH] Simple test
+From: Test Test <test@example.com>
+Date: Tue, 30 Aug 2022 11:19:07 -0400
+Message-Id: <orig-message@example.com>
+To: Some List <list-1@lists.example.com>
+Cc: Dev Eloper1 <dev-eloper1@example.com>, Dev Eloper2 <dev-eloper2@example.com>
+MIME-Version: 1.0
+Content-Type: text/plain; charset="utf-8"
+Content-Transfer-Encoding: 7bit
+
+Follow-up trailer collating test.
+
+Link: https://msgid.link/some@msgid.here
+Reviewed-by: Original Reviewer <original-reviewer@example.com>
+Signed-off-by: Original Submitter <original-submitter@example.com>
+Suggested-by: Friendly Suggester <suggested-by@example.com>
+Fixes: abcdef01234567890
+Link: https://lore.kernel.org/some@msgid.here  # bug discussion
+Reviewed-by: Followup Reviewer1 <followup-reviewer1@example.com>
+Tested-by: Followup Reviewer2 <followup-reviewer2@example.com>
+Cc: Dev Eloper1 <dev-eloper1@example.com>
+Cc: Dev Eloper2 <dev-eloper2@example.com>
+Cc: Some List <list-1@lists.example.com>
+Signed-off-by: Test Override <test-override@example.com>
+---
+
+diff --git a/b4/junk.py b/b4/junk.py
+index 12345678..23456789 100644
+--- a/b4/junk.py
+--- b/b4/junk.py
+@@@ -1,1 +1,1 @@ def junk():
+ 
+ 
+-junk1
++junk2
+ 
+ 
+-- 
+2.wong.fu
+
diff --git a/tests/samples/trailers-followup-custody.mbox b/tests/samples/trailers-followup-custody.mbox
new file mode 100644
index 0000000..0c4e4b8
--- /dev/null
+++ b/tests/samples/trailers-followup-custody.mbox
@@ -0,0 +1,65 @@
+From foo@z Thu Jan  1 00:00:00 1970
+From: Test Test <test@example.com>
+Subject: [PATCH] Simple test
+To: Some List <list-1@lists.example.com>
+Cc: Dev Eloper1 <dev-eloper1@example.com>,
+ Dev Eloper2 <dev-eloper2@example.com>
+Date: Tue, 30 Aug 2022 11:19:07 -0400
+Message-Id: <orig-message@example.com>
+
+Follow-up trailer collating test.
+
+Link: https://msgid.link/some@msgid.here
+Reviewed-by: Original Reviewer <original-reviewer@example.com>
+Signed-off-by: Original Submitter <original-submitter@example.com>
+Suggested-by: Friendly Suggester <suggested-by@example.com>
+Fixes: abcdef01234567890
+Link: https://lore.kernel.org/some@msgid.here  # bug discussion
+Signed-off-by: Test Override <test-override@example.com>
+---
+
+diff --git a/b4/junk.py b/b4/junk.py
+index 12345678..23456789 100644
+--- a/b4/junk.py
+--- b/b4/junk.py
+@@@ -1,1 +1,1 @@ def junk():
+ 
+ 
+-junk1
++junk2
+ 
+ 
+-- 
+2.wong.fu
+
+From foo@z Thu Jan  1 00:00:00 1970
+From: Followup Reviewer1 <followup-reviewer1@example.com>
+Subject: Re: [PATCH] Simple test
+Date: Tue, 30 Aug 2022 11:19:07 -0400
+Message-Id: <fwup-message-1@example.com>
+In-Reply-To: <orig-message@example.com>
+References: <orig-message@example.com>
+
+> This is a simple trailer parsing test.
+
+Reviewed-by: Followup Reviewer1 <followup-reviewer1@example.com>
+
+--
+My sig
+
+From foo@z Thu Jan  1 00:00:00 1970
+From: Followup Reviewer2 <followup-reviewer2@example.com>
+Subject: Re: [PATCH] Simple test
+Date: Tue, 30 Aug 2022 11:19:07 -0400
+Message-Id: <fwup-message-2@example.com>
+In-Reply-To: <fwup-message-1@example.com>
+References: <orig-message@example.com> <fwup-message-1@example.com>
+
+>> This is a simple trailer parsing test.
+> 
+> Reviewed-by: Followup Reviewer1 <reviewer1@example.com>
+
+Tested-by: Followup Reviewer2 <followup-reviewer2@example.com>
+
+--
+My sig
diff --git a/tests/samples/trailers-followup-single-ref-addlink.txt b/tests/samples/trailers-followup-single-ref-addlink.txt
new file mode 100644
index 0000000..024c842
--- /dev/null
+++ b/tests/samples/trailers-followup-single-ref-addlink.txt
@@ -0,0 +1,37 @@
+From git@z Thu Jan  1 00:00:00 1970
+Subject: [PATCH] Simple test
+From: Test Test <test@example.com>
+Date: Tue, 30 Aug 2022 11:19:07 -0400
+Message-Id: <orig-message@example.com>
+To: Some List <list-1@lists.example.com>
+Cc: Dev Eloper1 <dev-eloper1@example.com>, Dev Eloper2 <dev-eloper2@example.com>
+MIME-Version: 1.0
+Content-Type: text/plain; charset="utf-8"
+Content-Transfer-Encoding: 7bit
+
+Follow-up trailer collating test.
+
+Fixes: abcdef01234567890
+Reviewed-by: Original Reviewer <original-reviewer@example.com>
+Link: https://msgid.link/some@msgid.here
+Signed-off-by: Original Submitter <original-submitter@example.com>
+Reviewed-by: Followup Reviewer1 <followup-reviewer1@example.com>
+Tested-by: Followup Reviewer2 <followup-reviewer2@example.com>
+Link: https://lore.kernel.org/r/orig-message@example.com
+Signed-off-by: Test Override <test-override@example.com>
+---
+
+diff --git a/b4/junk.py b/b4/junk.py
+index 12345678..23456789 100644
+--- a/b4/junk.py
+--- b/b4/junk.py
+@@@ -1,1 +1,1 @@ def junk():
+ 
+ 
+-junk1
++junk2
+ 
+ 
+-- 
+2.wong.fu
+
diff --git a/tests/samples/trailers-followup-single-ref-addmysob.txt b/tests/samples/trailers-followup-single-ref-addmysob.txt
new file mode 100644
index 0000000..9da6c0b
--- /dev/null
+++ b/tests/samples/trailers-followup-single-ref-addmysob.txt
@@ -0,0 +1,36 @@
+From git@z Thu Jan  1 00:00:00 1970
+Subject: [PATCH] Simple test
+From: Test Test <test@example.com>
+Date: Tue, 30 Aug 2022 11:19:07 -0400
+Message-Id: <orig-message@example.com>
+To: Some List <list-1@lists.example.com>
+Cc: Dev Eloper1 <dev-eloper1@example.com>, Dev Eloper2 <dev-eloper2@example.com>
+MIME-Version: 1.0
+Content-Type: text/plain; charset="utf-8"
+Content-Transfer-Encoding: 7bit
+
+Follow-up trailer collating test.
+
+Fixes: abcdef01234567890
+Reviewed-by: Original Reviewer <original-reviewer@example.com>
+Link: https://msgid.link/some@msgid.here
+Signed-off-by: Original Submitter <original-submitter@example.com>
+Reviewed-by: Followup Reviewer1 <followup-reviewer1@example.com>
+Tested-by: Followup Reviewer2 <followup-reviewer2@example.com>
+Signed-off-by: Test Override <test-override@example.com>
+---
+
+diff --git a/b4/junk.py b/b4/junk.py
+index 12345678..23456789 100644
+--- a/b4/junk.py
+--- b/b4/junk.py
+@@@ -1,1 +1,1 @@ def junk():
+ 
+ 
+-junk1
++junk2
+ 
+ 
+-- 
+2.wong.fu
+
diff --git a/tests/samples/trailers-followup-single-ref-copyccs.txt b/tests/samples/trailers-followup-single-ref-copyccs.txt
new file mode 100644
index 0000000..3623462
--- /dev/null
+++ b/tests/samples/trailers-followup-single-ref-copyccs.txt
@@ -0,0 +1,39 @@
+From git@z Thu Jan  1 00:00:00 1970
+Subject: [PATCH] Simple test
+From: Test Test <test@example.com>
+Date: Tue, 30 Aug 2022 11:19:07 -0400
+Message-Id: <orig-message@example.com>
+To: Some List <list-1@lists.example.com>
+Cc: Dev Eloper1 <dev-eloper1@example.com>, Dev Eloper2 <dev-eloper2@example.com>
+MIME-Version: 1.0
+Content-Type: text/plain; charset="utf-8"
+Content-Transfer-Encoding: 7bit
+
+Follow-up trailer collating test.
+
+Fixes: abcdef01234567890
+Reviewed-by: Original Reviewer <original-reviewer@example.com>
+Link: https://msgid.link/some@msgid.here
+Signed-off-by: Original Submitter <original-submitter@example.com>
+Reviewed-by: Followup Reviewer1 <followup-reviewer1@example.com>
+Tested-by: Followup Reviewer2 <followup-reviewer2@example.com>
+Cc: Dev Eloper1 <dev-eloper1@example.com>
+Cc: Dev Eloper2 <dev-eloper2@example.com>
+Cc: Some List <list-1@lists.example.com>
+Signed-off-by: Test Override <test-override@example.com>
+---
+
+diff --git a/b4/junk.py b/b4/junk.py
+index 12345678..23456789 100644
+--- a/b4/junk.py
+--- b/b4/junk.py
+@@@ -1,1 +1,1 @@ def junk():
+ 
+ 
+-junk1
++junk2
+ 
+ 
+-- 
+2.wong.fu
+
diff --git a/tests/samples/trailers-followup-single-ref-defaults.txt b/tests/samples/trailers-followup-single-ref-defaults.txt
new file mode 100644
index 0000000..3750c06
--- /dev/null
+++ b/tests/samples/trailers-followup-single-ref-defaults.txt
@@ -0,0 +1,35 @@
+From git@z Thu Jan  1 00:00:00 1970
+Subject: [PATCH] Simple test
+From: Test Test <test@example.com>
+Date: Tue, 30 Aug 2022 11:19:07 -0400
+Message-Id: <orig-message@example.com>
+To: Some List <list-1@lists.example.com>
+Cc: Dev Eloper1 <dev-eloper1@example.com>, Dev Eloper2 <dev-eloper2@example.com>
+MIME-Version: 1.0
+Content-Type: text/plain; charset="utf-8"
+Content-Transfer-Encoding: 7bit
+
+Follow-up trailer collating test.
+
+Fixes: abcdef01234567890
+Reviewed-by: Original Reviewer <original-reviewer@example.com>
+Link: https://msgid.link/some@msgid.here
+Signed-off-by: Original Submitter <original-submitter@example.com>
+Reviewed-by: Followup Reviewer1 <followup-reviewer1@example.com>
+Tested-by: Followup Reviewer2 <followup-reviewer2@example.com>
+---
+
+diff --git a/b4/junk.py b/b4/junk.py
+index 12345678..23456789 100644
+--- a/b4/junk.py
+--- b/b4/junk.py
+@@@ -1,1 +1,1 @@ def junk():
+ 
+ 
+-junk1
++junk2
+ 
+ 
+-- 
+2.wong.fu
+
diff --git a/tests/samples/trailers-followup-single-ref-noadd.txt b/tests/samples/trailers-followup-single-ref-noadd.txt
new file mode 100644
index 0000000..80a1011
--- /dev/null
+++ b/tests/samples/trailers-followup-single-ref-noadd.txt
@@ -0,0 +1,33 @@
+From git@z Thu Jan  1 00:00:00 1970
+Subject: [PATCH] Simple test
+From: Test Test <test@example.com>
+Date: Tue, 30 Aug 2022 11:19:07 -0400
+Message-Id: <orig-message@example.com>
+To: Some List <list-1@lists.example.com>
+Cc: Dev Eloper1 <dev-eloper1@example.com>, Dev Eloper2 <dev-eloper2@example.com>
+MIME-Version: 1.0
+Content-Type: text/plain; charset="utf-8"
+Content-Transfer-Encoding: 7bit
+
+Follow-up trailer collating test.
+
+Fixes: abcdef01234567890
+Reviewed-by: Original Reviewer <original-reviewer@example.com>
+Link: https://msgid.link/some@msgid.here
+Signed-off-by: Original Submitter <original-submitter@example.com>
+---
+
+diff --git a/b4/junk.py b/b4/junk.py
+index 12345678..23456789 100644
+--- a/b4/junk.py
+--- b/b4/junk.py
+@@@ -1,1 +1,1 @@ def junk():
+ 
+ 
+-junk1
++junk2
+ 
+ 
+-- 
+2.wong.fu
+
diff --git a/tests/samples/trailers-followup-single-ref-ordered.txt b/tests/samples/trailers-followup-single-ref-ordered.txt
new file mode 100644
index 0000000..2084c36
--- /dev/null
+++ b/tests/samples/trailers-followup-single-ref-ordered.txt
@@ -0,0 +1,39 @@
+From git@z Thu Jan  1 00:00:00 1970
+Subject: [PATCH] Simple test
+From: Test Test <test@example.com>
+Date: Tue, 30 Aug 2022 11:19:07 -0400
+Message-Id: <orig-message@example.com>
+To: Some List <list-1@lists.example.com>
+Cc: Dev Eloper1 <dev-eloper1@example.com>, Dev Eloper2 <dev-eloper2@example.com>
+MIME-Version: 1.0
+Content-Type: text/plain; charset="utf-8"
+Content-Transfer-Encoding: 7bit
+
+Follow-up trailer collating test.
+
+Fixes: abcdef01234567890
+Reviewed-by: Original Reviewer <original-reviewer@example.com>
+Link: https://msgid.link/some@msgid.here
+Signed-off-by: Original Submitter <original-submitter@example.com>
+Cc: Dev Eloper1 <dev-eloper1@example.com>
+Cc: Dev Eloper2 <dev-eloper2@example.com>
+Cc: Some List <list-1@lists.example.com>
+Tested-by: Followup Reviewer2 <followup-reviewer2@example.com>
+Reviewed-by: Followup Reviewer1 <followup-reviewer1@example.com>
+Signed-off-by: Test Override <test-override@example.com>
+---
+
+diff --git a/b4/junk.py b/b4/junk.py
+index 12345678..23456789 100644
+--- a/b4/junk.py
+--- b/b4/junk.py
+@@@ -1,1 +1,1 @@ def junk():
+ 
+ 
+-junk1
++junk2
+ 
+ 
+-- 
+2.wong.fu
+
diff --git a/tests/samples/trailers-followup-single-ref-sloppy.txt b/tests/samples/trailers-followup-single-ref-sloppy.txt
new file mode 100644
index 0000000..9b6a49d
--- /dev/null
+++ b/tests/samples/trailers-followup-single-ref-sloppy.txt
@@ -0,0 +1,37 @@
+From git@z Thu Jan  1 00:00:00 1970
+Subject: [PATCH] Simple test
+From: Test Test <test@example.com>
+Date: Tue, 30 Aug 2022 11:19:07 -0400
+Message-Id: <orig-message@example.com>
+To: Some List <list-1@lists.example.com>
+Cc: Dev Eloper1 <dev-eloper1@example.com>, Dev Eloper2 <dev-eloper2@example.com>
+MIME-Version: 1.0
+Content-Type: text/plain; charset="utf-8"
+Content-Transfer-Encoding: 7bit
+
+Follow-up trailer collating test.
+
+Fixes: abcdef01234567890
+Reviewed-by: Original Reviewer <original-reviewer@example.com>
+Link: https://msgid.link/some@msgid.here
+Signed-off-by: Original Submitter <original-submitter@example.com>
+Reviewed-by: Followup Reviewer1 <followup-reviewer1@example.com>
+Tested-by: Followup Reviewer2 <followup-reviewer2@example.com>
+Reviewed-by: Mismatched Reviewer1 <mismatched-reviewer1@example.net>
+Signed-off-by: Test Override <test-override@example.com>
+---
+
+diff --git a/b4/junk.py b/b4/junk.py
+index 12345678..23456789 100644
+--- a/b4/junk.py
+--- b/b4/junk.py
+@@@ -1,1 +1,1 @@ def junk():
+ 
+ 
+-junk1
++junk2
+ 
+ 
+-- 
+2.wong.fu
+
diff --git a/tests/samples/trailers-followup-single.mbox b/tests/samples/trailers-followup-single.mbox
new file mode 100644
index 0000000..b12f6ba
--- /dev/null
+++ b/tests/samples/trailers-followup-single.mbox
@@ -0,0 +1,78 @@
+From foo@z Thu Jan  1 00:00:00 1970
+From: Test Test <test@example.com>
+Subject: [PATCH] Simple test
+To: Some List <list-1@lists.example.com>
+Cc: Dev Eloper1 <dev-eloper1@example.com>,
+ Dev Eloper2 <dev-eloper2@example.com>
+Date: Tue, 30 Aug 2022 11:19:07 -0400
+Message-Id: <orig-message@example.com>
+
+Follow-up trailer collating test.
+
+Fixes: abcdef01234567890
+Reviewed-by: Original Reviewer <original-reviewer@example.com>
+Link: https://msgid.link/some@msgid.here
+Signed-off-by: Original Submitter <original-submitter@example.com>
+---
+
+diff --git a/b4/junk.py b/b4/junk.py
+index 12345678..23456789 100644
+--- a/b4/junk.py
+--- b/b4/junk.py
+@@@ -1,1 +1,1 @@ def junk():
+ 
+ 
+-junk1
++junk2
+ 
+ 
+-- 
+2.wong.fu
+
+From foo@z Thu Jan  1 00:00:00 1970
+From: Followup Reviewer1 <followup-reviewer1@example.com>
+Subject: Re: [PATCH] Simple test
+Date: Tue, 30 Aug 2022 11:19:07 -0400
+Message-Id: <fwup-message-1@example.com>
+In-Reply-To: <orig-message@example.com>
+References: <orig-message@example.com>
+
+> This is a simple trailer parsing test.
+
+Reviewed-by: Followup Reviewer1 <followup-reviewer1@example.com>
+
+--
+My sig
+
+From foo@z Thu Jan  1 00:00:00 1970
+From: Followup Reviewer2 <followup-reviewer2@example.com>
+Subject: Re: [PATCH] Simple test
+Date: Tue, 30 Aug 2022 11:19:07 -0400
+Message-Id: <fwup-message-2@example.com>
+In-Reply-To: <fwup-message-1@example.com>
+References: <orig-message@example.com> <fwup-message-1@example.com>
+
+>> This is a simple trailer parsing test.
+> 
+> Reviewed-by: Followup Reviewer1 <reviewer1@example.com>
+
+Tested-by: Followup Reviewer2 <followup-reviewer2@example.com>
+
+--
+My sig
+
+From foo@z Thu Jan  1 00:00:00 1970
+From: Mismatched Reviewer <mismatched-reviewer1@example.com>
+Subject: Re: [PATCH] Simple test
+Date: Tue, 30 Aug 2022 11:19:07 -0400
+Message-Id: <fwup-message-3@example.com>
+In-Reply-To: <orig-message@example.com>
+References: <orig-message@example.com>
+
+> This is a simple trailer parsing test.
+
+Reviewed-by: Mismatched Reviewer1 <mismatched-reviewer1@example.net>
+
+--
+My sig
+
diff --git a/tests/samples/trailers-followup-with-cover-ref-covertrailers.txt b/tests/samples/trailers-followup-with-cover-ref-covertrailers.txt
new file mode 100644
index 0000000..8a503ea
--- /dev/null
+++ b/tests/samples/trailers-followup-with-cover-ref-covertrailers.txt
@@ -0,0 +1,75 @@
+From git@z Thu Jan  1 00:00:00 1970
+Subject: [PATCH v2 1/2] Simple test 1
+From: Test Test <test@example.com>
+Date: Tue, 30 Aug 2022 11:19:07 -0400
+Message-Id: <patch-1-message@example.com>
+To: Some List <list-1@lists.example.com>
+Cc: Dev Eloper1 <dev-eloper1@example.com>, Dev Eloper2 <dev-eloper2@example.com>
+In-Reply-To: <cover-message@example.com>
+References: <cover-message@example.com>
+MIME-Version: 1.0
+Content-Type: text/plain; charset="utf-8"
+Content-Transfer-Encoding: 7bit
+
+Follow-up trailer collating test patch 1.
+
+Fixes: abcdef01234567890
+Reviewed-by: Original Reviewer <original-reviewer@example.com>
+Link: https://msgid.link/some@msgid.here
+Signed-off-by: Original Submitter <original-submitter@example.com>
+Reviewed-by: Coverletter Reviewer1 <followup-reviewer1@example.com>
+Signed-off-by: Test Override <test-override@example.com>
+---
+
+diff --git a/b4/junk.py b/b4/junk.py
+index 12345678..23456789 100644
+--- a/b4/junk.py
+--- b/b4/junk.py
+@@@ -1,1 +1,1 @@ def junk():
+ 
+ 
+-junk1
++junk2
+ 
+ 
+-- 
+2.wong.fu
+
+From git@z Thu Jan  1 00:00:00 1970
+Subject: [PATCH v2 2/2] Simple test 2
+From: Test Test <test@example.com>
+Date: Tue, 30 Aug 2022 11:19:07 -0400
+Message-Id: <patch-2-message@example.com>
+To: Some List <list-1@lists.example.com>
+Cc: Dev Eloper1 <dev-eloper1@example.com>, Dev Eloper2 <dev-eloper2@example.com>
+In-Reply-To: <cover-message@example.com>
+References: <cover-message@example.com>
+MIME-Version: 1.0
+Content-Type: text/plain; charset="utf-8"
+Content-Transfer-Encoding: 7bit
+
+Follow-up trailer collating test patch 2.
+
+Fixes: abcdef01234567890
+Reviewed-by: Original Reviewer <original-reviewer@example.com>
+Link: https://msgid.link/some@msgid.here
+Signed-off-by: Original Submitter <original-submitter@example.com>
+Reviewed-by: Followup Reviewer1 <followup-reviewer1@example.com>
+Reviewed-by: Coverletter Reviewer1 <followup-reviewer1@example.com>
+Signed-off-by: Test Override <test-override@example.com>
+---
+
+diff --git a/b4/bupkes.py b/b4/bupkes.py
+index 12345678..23456789 100644
+--- a/b4/bupkes.py
+--- b/b4/bupkes.py
+@@@ -1,1 +1,1 @@ def bupkes():
+ 
+ 
+-bupkes1
++bupkes2
+ 
+ 
+-- 
+2.wong.fu
+
diff --git a/tests/samples/trailers-followup-with-cover-ref-defaults.txt b/tests/samples/trailers-followup-with-cover-ref-defaults.txt
new file mode 100644
index 0000000..cbd1eb8
--- /dev/null
+++ b/tests/samples/trailers-followup-with-cover-ref-defaults.txt
@@ -0,0 +1,73 @@
+From git@z Thu Jan  1 00:00:00 1970
+Subject: [PATCH v2 1/2] Simple test 1
+From: Test Test <test@example.com>
+Date: Tue, 30 Aug 2022 11:19:07 -0400
+Message-Id: <patch-1-message@example.com>
+To: Some List <list-1@lists.example.com>
+Cc: Dev Eloper1 <dev-eloper1@example.com>, Dev Eloper2 <dev-eloper2@example.com>
+In-Reply-To: <cover-message@example.com>
+References: <cover-message@example.com>
+MIME-Version: 1.0
+Content-Type: text/plain; charset="utf-8"
+Content-Transfer-Encoding: 7bit
+
+Follow-up trailer collating test patch 1.
+
+Fixes: abcdef01234567890
+Reviewed-by: Original Reviewer <original-reviewer@example.com>
+Link: https://msgid.link/some@msgid.here
+Signed-off-by: Original Submitter <original-submitter@example.com>
+Signed-off-by: Test Override <test-override@example.com>
+---
+
+diff --git a/b4/junk.py b/b4/junk.py
+index 12345678..23456789 100644
+--- a/b4/junk.py
+--- b/b4/junk.py
+@@@ -1,1 +1,1 @@ def junk():
+ 
+ 
+-junk1
++junk2
+ 
+ 
+-- 
+2.wong.fu
+
+From git@z Thu Jan  1 00:00:00 1970
+Subject: [PATCH v2 2/2] Simple test 2
+From: Test Test <test@example.com>
+Date: Tue, 30 Aug 2022 11:19:07 -0400
+Message-Id: <patch-2-message@example.com>
+To: Some List <list-1@lists.example.com>
+Cc: Dev Eloper1 <dev-eloper1@example.com>, Dev Eloper2 <dev-eloper2@example.com>
+In-Reply-To: <cover-message@example.com>
+References: <cover-message@example.com>
+MIME-Version: 1.0
+Content-Type: text/plain; charset="utf-8"
+Content-Transfer-Encoding: 7bit
+
+Follow-up trailer collating test patch 2.
+
+Fixes: abcdef01234567890
+Reviewed-by: Original Reviewer <original-reviewer@example.com>
+Link: https://msgid.link/some@msgid.here
+Signed-off-by: Original Submitter <original-submitter@example.com>
+Reviewed-by: Followup Reviewer1 <followup-reviewer1@example.com>
+Signed-off-by: Test Override <test-override@example.com>
+---
+
+diff --git a/b4/bupkes.py b/b4/bupkes.py
+index 12345678..23456789 100644
+--- a/b4/bupkes.py
+--- b/b4/bupkes.py
+@@@ -1,1 +1,1 @@ def bupkes():
+ 
+ 
+-bupkes1
++bupkes2
+ 
+ 
+-- 
+2.wong.fu
+
diff --git a/tests/samples/trailers-followup-with-cover.mbox b/tests/samples/trailers-followup-with-cover.mbox
new file mode 100644
index 0000000..52c14c4
--- /dev/null
+++ b/tests/samples/trailers-followup-with-cover.mbox
@@ -0,0 +1,113 @@
+From foo@z Thu Jan  1 00:00:00 1970
+From: Test Test <test@example.com>
+Subject: [PATCH v2 0/2] Simple cover
+To: Some List <list-1@lists.example.com>
+Cc: Dev Eloper1 <dev-eloper1@example.com>,
+ Dev Eloper2 <dev-eloper2@example.com>
+Date: Tue, 30 Aug 2022 11:19:07 -0400
+Message-Id: <cover-message@example.com>
+
+This is a cover letter. It has a diffstat.
+
+---
+b4/junk.py    |  1 -
+b4/bupkes.py  |  1 -
+2 files changed, 2 insertions(+), 2 deletions(-)
+
+
+From foo@z Thu Jan  1 00:00:00 1970
+From: Test Test <test@example.com>
+Subject: [PATCH v2 1/2] Simple test 1
+To: Some List <list-1@lists.example.com>
+Cc: Dev Eloper1 <dev-eloper1@example.com>,
+ Dev Eloper2 <dev-eloper2@example.com>
+Date: Tue, 30 Aug 2022 11:19:07 -0400
+Message-Id: <patch-1-message@example.com>
+In-Reply-To: <cover-message@example.com>
+References: <cover-message@example.com>
+
+Follow-up trailer collating test patch 1.
+
+Fixes: abcdef01234567890
+Reviewed-by: Original Reviewer <original-reviewer@example.com>
+Link: https://msgid.link/some@msgid.here
+Signed-off-by: Original Submitter <original-submitter@example.com>
+---
+
+diff --git a/b4/junk.py b/b4/junk.py
+index 12345678..23456789 100644
+--- a/b4/junk.py
+--- b/b4/junk.py
+@@@ -1,1 +1,1 @@ def junk():
+ 
+ 
+-junk1
++junk2
+ 
+ 
+-- 
+2.wong.fu
+
+From foo@z Thu Jan  1 00:00:00 1970
+From: Test Test <test@example.com>
+Subject: [PATCH v2 2/2] Simple test 2
+To: Some List <list-1@lists.example.com>
+Cc: Dev Eloper1 <dev-eloper1@example.com>,
+ Dev Eloper2 <dev-eloper2@example.com>
+Date: Tue, 30 Aug 2022 11:19:07 -0400
+Message-Id: <patch-2-message@example.com>
+In-Reply-To: <cover-message@example.com>
+References: <cover-message@example.com>
+
+Follow-up trailer collating test patch 2.
+
+Fixes: abcdef01234567890
+Reviewed-by: Original Reviewer <original-reviewer@example.com>
+Link: https://msgid.link/some@msgid.here
+Signed-off-by: Original Submitter <original-submitter@example.com>
+---
+
+diff --git a/b4/bupkes.py b/b4/bupkes.py
+index 12345678..23456789 100644
+--- a/b4/bupkes.py
+--- b/b4/bupkes.py
+@@@ -1,1 +1,1 @@ def bupkes():
+ 
+ 
+-bupkes1
++bupkes2
+ 
+ 
+-- 
+2.wong.fu
+
+From foo@z Thu Jan  1 00:00:00 1970
+From: Followup Reviewer1 <followup-reviewer1@example.com>
+Subject: Re: [PATCH v2 2/2] Simple test 2
+Date: Tue, 30 Aug 2022 11:19:07 -0400
+Message-Id: <fwup-message-1@example.com>
+In-Reply-To: <patch-2-message@example.com>
+References: <patch-2-message@example.com> <cover-message@example.com>
+
+> This is a simple trailer parsing test.
+
+Reviewed-by: Followup Reviewer1 <followup-reviewer1@example.com>
+
+--
+My sig
+
+From foo@z Thu Jan  1 00:00:00 1970
+From: Followup Reviewer1 <followup-reviewer1@example.com>
+Subject: Re: [PATCH v2 0/2] Simple cover
+Date: Tue, 30 Aug 2022 11:19:07 -0400
+Message-Id: <fwup-message-2@example.com>
+In-Reply-To: <cover-message@example.com>
+References: <cover-message@example.com>
+
+> This is a simple trailer parsing test.
+
+Reviewed-by: Coverletter Reviewer1 <followup-reviewer1@example.com>
+
+--
+My sig
+
diff --git a/tests/samples/trailers-test-extinfo.txt b/tests/samples/trailers-test-extinfo.txt
new file mode 100644
index 0000000..d36abbb
--- /dev/null
+++ b/tests/samples/trailers-test-extinfo.txt
@@ -0,0 +1,29 @@
+From: Test Test <test@example.com>
+Subject: [PATCH] Simple test
+Date: Tue, 30 Aug 2022 11:19:07 -0400
+
+This is a simple trailer parsing test.
+
+Reviewed-by: Bogus Bupkes <bogus@example.com>
+[for the parts that are bogus]
+Fixes: abcdef01234567890
+Tested-by: Some Person <bogus2@example.com>
+           [this person visually indented theirs]
+Link: https://msgid.link/some@msgid.here  # initial submission
+Signed-off-by: Wrapped Persontrailer
+<broken@example.com>
+---
+
+diff --git a/b4/junk.py b/b4/junk.py
+index 12345678..23456789 100644
+--- a/b4/junk.py
+--- b/b4/junk.py
+@@@ -1,1 +1,1 @@ def junk():
+ 
+ 
+-junk1
++junk2
+ 
+ 
+-- 
+2.wong.fu
diff --git a/tests/samples/trailers-test-simple.txt b/tests/samples/trailers-test-simple.txt
new file mode 100644
index 0000000..693d781
--- /dev/null
+++ b/tests/samples/trailers-test-simple.txt
@@ -0,0 +1,24 @@
+From: Test Test <test@example.com>
+Subject: [PATCH] Simple test
+Date: Tue, 30 Aug 2022 11:19:07 -0400
+
+This is a simple trailer parsing test.
+
+Reviewed-by: Bogus Bupkes <bogus@example.com>
+Fixes: abcdef01234567890
+Link: https://msgid.link/some@msgid.here
+---
+
+diff --git a/b4/junk.py b/b4/junk.py
+index 12345678..23456789 100644
+--- a/b4/junk.py
+--- b/b4/junk.py
+@@@ -1,1 +1,1 @@ def junk():
+ 
+ 
+-junk1
++junk2
+ 
+ 
+-- 
+2.wong.fu