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>

17 files changed, 859 insertions, 2 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
diff --git a/tests/test___init__.py b/tests/test___init__.py
index d78667e..f97e166 100644
--- a/tests/test___init__.py
+++ b/tests/test___init__.py
@@ -1,7 +1,9 @@
 import pytest  # noqa
 import b4
-import re
 import os
+import email
+import mailbox
+import io
 
 
 @pytest.mark.parametrize('source,expected', [
@@ -25,7 +27,6 @@ def test_save_git_am_mbox(tmpdir, source, regex, flags, ismbox):
     import re
     if source is not None:
         if ismbox:
-            import mailbox
             mbx = mailbox.mbox(f'tests/samples/{source}.txt')
             msgs = list(mbx)
         else:
@@ -48,3 +49,64 @@ def test_save_git_am_mbox(tmpdir, source, regex, flags, ismbox):
     with open(dest, 'r') as fh:
         res = fh.read()
     assert re.search(regex, res, flags=flags)
+
+
+@pytest.mark.parametrize('source,expected', [
+    ('trailers-test-simple',
+     [('person', 'Reviewed-By', 'Bogus Bupkes <bogus@example.com>', None),
+      ('utility', 'Fixes', 'abcdef01234567890', None),
+      ('utility', 'Link', 'https://msgid.link/some@msgid.here', None),
+      ]),
+    ('trailers-test-extinfo',
+     [('person', 'Reviewed-by', 'Bogus Bupkes <bogus@example.com>', '[for the parts that are bogus]'),
+      ('utility', 'Fixes', 'abcdef01234567890', None),
+      ('person', 'Tested-by', 'Some Person <bogus2@example.com>', '           [this person visually indented theirs]'),
+      ('utility', 'Link', 'https://msgid.link/some@msgid.here', '  # initial submission'),
+      ('person', 'Signed-off-by', 'Wrapped Persontrailer <broken@example.com>', None),
+      ]),
+])
+def test_parse_trailers(source, expected):
+    with open(f'tests/samples/{source}.txt', 'r') as fh:
+        msg = email.message_from_file(fh)
+        lmsg = b4.LoreMessage(msg)
+        gh, m, trs, bas, sig = b4.LoreMessage.get_body_parts(lmsg.body)
+        assert len(expected) == len(trs)
+        for tr in trs:
+            mytype, myname, myvalue, myextinfo = expected.pop(0)
+            mytr = b4.LoreTrailer(name=myname, value=myvalue, extinfo=myextinfo)
+            assert tr == mytr
+            assert tr.type == mytype
+
+
+@pytest.mark.parametrize('source,serargs,amargs,reference,b4cfg', [
+    ('single', {}, {}, 'defaults', {}),
+    ('single', {}, {'noaddtrailers': True}, 'noadd', {}),
+    ('single', {}, {'addmysob': True}, 'addmysob', {}),
+    ('single', {}, {'addmysob': True, 'copyccs': True}, 'copyccs', {}),
+    ('single', {}, {'addmysob': True, 'addlink': True}, 'addlink', {}),
+    ('single', {}, {'addmysob': True, 'copyccs': True}, 'ordered',
+     {'trailer-order': 'Cc,Tested*,Reviewed*,*'}),
+    ('single', {'sloppytrailers': True}, {'addmysob': True}, 'sloppy', {}),
+    ('with-cover', {}, {'addmysob': True}, 'defaults', {}),
+    ('with-cover', {}, {'covertrailers': True, 'addmysob': True}, 'covertrailers', {}),
+    ('custody', {}, {'addmysob': True, 'copyccs': True}, 'unordered', {}),
+    ('custody', {}, {'addmysob': True, 'copyccs': True}, 'ordered',
+     {'trailer-order': 'Cc,Fixes*,Link*,Suggested*,Reviewed*,Tested*,*'}),
+])
+def test_followup_trailers(source, serargs, amargs, reference, b4cfg):
+    b4.USER_CONFIG = {
+        'name': 'Test Override',
+        'email': 'test-override@example.com',
+    }
+    b4.MAIN_CONFIG = dict(b4.DEFAULT_CONFIG)
+    b4.MAIN_CONFIG.update(b4cfg)
+    lmbx = b4.LoreMailbox()
+    for msg in mailbox.mbox(f'tests/samples/trailers-followup-{source}.mbox'):
+        lmbx.add_message(msg)
+    lser = lmbx.get_series(**serargs)
+    assert lser is not None
+    amsgs = lser.get_am_ready(**amargs)
+    ifh = io.StringIO()
+    b4.save_git_am_mbox(amsgs, ifh)
+    with open(f'tests/samples/trailers-followup-{source}-ref-{reference}.txt', 'r') as fh:
+        assert ifh.getvalue() == fh.read()