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>

21 files changed, 1112 insertions, 153 deletions

diff --git a/b4/__init__.py b/b4/__init__.py
index 84ef073..e8e31fe 100644
--- a/b4/__init__.py
+++ b/b4/__init__.py
@@ -304,14 +304,14 @@ class LoreMailbox:
                 continue
 
             trailers, mismatches = fmsg.get_trailers(sloppy=sloppytrailers)
-            for trailer in mismatches:
-                lser.trailer_mismatches.add((trailer[0], trailer[1], fmsg.fromname, fmsg.fromemail))
+            for ltr in mismatches:
+                lser.trailer_mismatches.add((ltr.name, ltr.value, fmsg.fromname, fmsg.fromemail))
             lvl = 1
             while True:
                 logger.debug('%sParent: %s', ' ' * lvl, pmsg.full_subject)
                 logger.debug('%sTrailers:', ' ' * lvl)
-                for trailer in trailers:
-                    logger.debug('%s%s: %s', ' ' * (lvl+1), trailer[0], trailer[1])
+                for ltr in trailers:
+                    logger.debug('%s%s: %s', ' ' * (lvl+1), ltr.name, ltr.value)
                 if pmsg.has_diff and not pmsg.reply:
                     # We found the patch for these trailers
                     if pmsg.revision != revision:
@@ -330,9 +330,9 @@ class LoreMailbox:
                     break
                 if pmsg.in_reply_to and pmsg.in_reply_to in self.msgid_map:
                     lvl += 1
-                    for ptrailer in pmsg.trailers:
-                        print(ptrailer)
-                        trailers.append(tuple(ptrailer + (pmsg,)))
+                    for pltr in pmsg.trailers:
+                        pltr.lmsg = pmsg
+                        trailers.append(pltr)
                     pmsg = self.msgid_map[pmsg.in_reply_to]
                     continue
                 break
@@ -557,11 +557,13 @@ class LoreSeries:
                     raise KeyError('Cherrypick not in series')
 
             if lmsg is not None:
+                extras = list()
                 if addlink:
-                    lmsg.followup_trailers.append(('Link', linkmask % lmsg.msgid, None, None))
-                if addmysob:
-                    lmsg.followup_trailers.append(('Signed-off-by',
-                                                   '%s <%s>' % (usercfg['name'], usercfg['email']), None, None))
+                    if linkmask is None:
+                        linkmask = config.get('linkmask')
+                    linkval = linkmask % lmsg.msgid
+                    lltr = LoreTrailer(name='Link', value=linkval)
+                    extras.append(lltr)
 
                 if attsame and not attcrit:
                     if attmark:
@@ -588,7 +590,8 @@ class LoreSeries:
                 add_trailers = True
                 if noaddtrailers:
                     add_trailers = False
-                msg = lmsg.get_am_message(add_trailers=add_trailers, copyccs=copyccs, allowbadchars=allowbadchars)
+                msg = lmsg.get_am_message(add_trailers=add_trailers, extras=extras, copyccs=copyccs,
+                                          addmysob=addmysob, allowbadchars=allowbadchars)
                 msgs.append(msg)
             else:
                 logger.error('  ERROR: missing [%s/%s]!', at, self.expected)
@@ -832,6 +835,101 @@ class LoreSeries:
         logger.critical('Cover: %s', outfile)
 
 
+class LoreTrailer:
+    type: str
+    name: str
+    lname: str
+    value: str
+    extinfo: Optional[str] = None
+    addr: Optional[Tuple[str, str]] = None
+    lmsg = None
+    # Small list of recognized utility trailers
+    _utility: Set[str] = {'fixes', 'link', 'buglink', 'obsoleted-by', 'message-id', 'change-id'}
+
+    def __init__(self, name: Optional[str] = None, value: Optional[str] = None, extinfo: Optional[str] = None,
+                 msg: Optional[email.message.Message] = None):
+        if name is None:
+            self.name = 'Signed-off-by'
+            ucfg = get_user_config()
+            self.value = '%s <%s>' % (ucfg['name'], ucfg['email'])
+            self.type = 'person'
+            self.addr = (ucfg['name'], ucfg['email'])
+        else:
+            self.name = name
+            self.value = value
+            if name.lower() in self._utility:
+                self.type = 'utility'
+            elif re.search(r'\S+@\S+\.\S+', value):
+                self.type = 'person'
+                self.addr = email.utils.parseaddr(value)
+            else:
+                self.type = 'unknown'
+        self.lname = self.name.lower()
+        self.extinfo = extinfo
+        self.msg = msg
+
+    def as_string(self, omit_extinfo: bool = False) -> str:
+        ret = f'{self.name}: {self.value}'
+        if not self.extinfo or omit_extinfo:
+            return ret
+        # extinfo can be either be [on the next line], or  # at the end
+        if self.extinfo.lstrip()[0] == '#':
+            ret += self.extinfo
+        else:
+            ret += f'\n{self.extinfo}'
+
+        return ret
+
+    def email_eq(self, cmp_email: str, fuzzy: bool = True) -> bool:
+        if not self.addr:
+            return False
+        our = self.addr[1].lower()
+        their = cmp_email.lower()
+        if our == their:
+            return True
+        if not fuzzy:
+            return False
+
+        if '@' not in our or '@' not in their:
+            return False
+
+        # Strip extended local parts often added by people, e.g.:
+        # comparing foo@example.com and foo+kernel@example.com should match
+        our = re.sub(r'\+[^@]+@', '@', our)
+        their = re.sub(r'\+[^@]+@', '@', their)
+        if our == their:
+            return True
+
+        # See if domain part of one of the addresses is a subset of the other one,
+        # which should match cases like foo@linux.intel.com and foo@intel.com
+        olocal, odomain = our.split('@', maxsplit=1)
+        tlocal, tdomain = their.split('@', maxsplit=1)
+        if olocal != tlocal:
+            return False
+
+        if (abs(odomain.count('.')-tdomain.count('.')) == 1
+                and (odomain.endswith(f'.{tdomain}') or tdomain.endswith(f'.{odomain}'))):
+            return True
+
+        return False
+
+    def __eq__(self, other):
+        # We never compare extinfo, we just tack it if we find a match
+        return self.lname == other.lname and self.value.lower() == other.value.lower()
+
+    def __hash__(self):
+        return hash(f'{self.lname}: {self.value}')
+
+    def __repr__(self):
+        out = list()
+        out.append('  type: %s' % self.type)
+        out.append('  name: %s' % self.name)
+        out.append('  value: %s' % self.value)
+        out.append('  extinfo: %s' % self.extinfo)
+
+        return '\n'.join(out)
+
+
 class LoreMessage:
     def __init__(self, msg):
         self.msg = msg
@@ -971,41 +1069,32 @@ class LoreMessage:
             trailers, others = LoreMessage.find_trailers(self.body, followup=True)
             for trailer in trailers:
                 # These are commonly part of patch/commit metadata
-                badtrailers = ('from', 'author', 'cc', 'to')
-                if trailer[0].lower() not in badtrailers:
+                badtrailers = {'from', 'author', 'cc', 'to'}
+                if trailer.lname not in badtrailers:
                     self.trailers.append(trailer)
 
-    def get_trailers(self, sloppy=False):
+    def get_trailers(self, sloppy: bool = False) -> Tuple[List[LoreTrailer], List[LoreTrailer]]:
         trailers = list()
-        mismatches = set()
+        mismatches = list()
 
-        for tname, tvalue, extdata in self.trailers:
-            if sloppy or tname.lower() in ('fixes', 'obsoleted-by'):
-                trailers.append((tname, tvalue, extdata, self))
+        for ltr in self.trailers:
+            ltr.lmsg = self
+            if sloppy or ltr.type != 'person':
+                trailers.append(ltr)
                 continue
 
-            tmatch = False
-            namedata = email.utils.getaddresses([tvalue])[0]
-            tfrom = re.sub(r'\+[^@]+@', '@', namedata[1].lower())
-            hfrom = re.sub(r'\+[^@]+@', '@', self.fromemail.lower())
-            tlname = namedata[0].lower()
-            hlname = self.fromname.lower()
-            tchunks = tfrom.split('@')
-            hchunks = hfrom.split('@')
-            if tfrom == hfrom:
-                logger.debug('  trailer exact email match')
-                tmatch = True
-            # See if domain part of one of the addresses is a subset of the other one,
-            # which should match cases like @linux.intel.com and @intel.com
-            elif (len(tchunks) == 2 and len(hchunks) == 2
-                  and tchunks[0] == hchunks[0]
-                  and (tchunks[1].find(hchunks[1]) >= 0 or hchunks[1].find(tchunks[1]) >= 0)):
-                logger.debug('  trailer fuzzy email match')
-                tmatch = True
+            if ltr.email_eq(self.fromemail):
+                logger.debug('  trailer email match')
+                trailers.append(ltr)
+
             # Does the name match, at least?
-            elif tlname == hlname:
+            nmatch = False
+            tlname = ltr.addr[0].lower()
+            hlname = self.fromname.lower()
+
+            if tlname == hlname:
                 logger.debug('  trailer exact name match')
-                tmatch = True
+                nmatch = True
             # Finally, see if the header From has a comma in it and try to find all
             # parts in the trailer name
             elif hlname.find(',') > 0:
@@ -1014,13 +1103,12 @@ class LoreMessage:
                     if hlname.find(nchunk.strip()) < 0:
                         nmatch = False
                         break
-                if nmatch:
-                    logger.debug('  trailer fuzzy name match')
-                    tmatch = True
-            if tmatch:
-                trailers.append((tname, tvalue, extdata, self))
-            else:
-                mismatches.add((tname, tvalue, extdata, self))
+            if nmatch:
+                logger.debug('  trailer fuzzy name match')
+                trailers.append(ltr)
+                continue
+
+            mismatches.append(ltr)
 
         return trailers, mismatches
 
@@ -1409,7 +1497,7 @@ class LoreMessage:
         return indexes
 
     @staticmethod
-    def find_trailers(body: str, followup: bool = False) -> Tuple[List[Tuple], List[str]]:
+    def find_trailers(body: str, followup: bool = False) -> Tuple[List[LoreTrailer], List[str]]:
         ignores = {'phone', 'email'}
         headers = {'subject', 'date', 'from'}
         nonperson = {'fixes', 'subject', 'date', 'link', 'buglink', 'obsoleted-by'}
@@ -1434,43 +1522,51 @@ class LoreMessage:
             line = line.strip('\r')
             matches = re.search(r'^\s*(\w\S+):\s+(\S.*)', line, flags=re.I)
             if matches:
-                groups = list(matches.groups())
+                oname, ovalue = list(matches.groups())
                 # We only accept headers if we haven't seen any non-trailer lines
-                tname = groups[0].lower()
-                if tname in ignores:
+                lname = oname.lower()
+                if lname in ignores:
                     logger.debug('Ignoring known non-trailer: %s', line)
                     continue
-                if len(others) and tname in headers:
+                if len(others) and lname in headers:
                     logger.debug('Ignoring %s (header after other content)', line)
                     continue
                 if followup:
-                    if not tname.isascii():
-                        logger.debug('Ignoring known non-ascii follow-up trailer: %s', tname)
+                    if not lname.isascii():
+                        logger.debug('Ignoring known non-ascii follow-up trailer: %s', lname)
                         continue
-                    mperson = re.search(r'\S+@\S+\.\S+', groups[1])
-                    if not mperson and tname not in nonperson:
+                    mperson = re.search(r'\S+@\S+\.\S+', ovalue)
+                    if not mperson and lname not in nonperson:
                         logger.debug('Ignoring %s (not a recognized non-person trailer)', line)
                         continue
+
+                extinfo = None
+                mextinfo = re.search(r'(.*\S+)(\s+#[^#]+)$', ovalue)
+                if mextinfo:
+                    logger.debug('Trailer contains hashtag extinfo: ', line)
+                    # Found extinfo of the hashtag genre
+                    egr = mextinfo.groups()
+                    ovalue = egr[0]
+                    extinfo = egr[1]
+
                 was_trailer = True
-                groups.append(None)
-                trailers.append(groups)
+                ltrailer = LoreTrailer(name=oname, value=ovalue, extinfo=extinfo)
+                trailers.append(ltrailer)
                 continue
             # Is it an extended info line, e.g.:
             # Signed-off-by: Foo Foo <foo@foo.com>
             # [for the foo bits]
-            if len(line) > 2 and line[0] == '[' and line[-1] == ']' and was_trailer:
-                trailers[-1][2] = line
+            if len(line) > 2 and was_trailer and re.search(r'^\s*\[[^]]+]\s*$', line):
+                trailers[-1].extinfo = line
                 was_trailer = False
                 continue
             was_trailer = False
             others.append(line)
 
-        # convert to tuples for ease of matching
-        ttrailers = [tuple(x) for x in trailers]
-        return ttrailers, others
+        return trailers, others
 
     @staticmethod
-    def get_body_parts(body):
+    def get_body_parts(body: str) -> Tuple[List[LoreTrailer], str, List[LoreTrailer], str, str]:
         # remove any starting/trailing blank lines
         body = body.replace('\r', '')
         body = body.strip('\n')
@@ -1533,13 +1629,28 @@ class LoreMessage:
 
         return githeaders, message, trailers, basement, signature
 
-    def fix_trailers(self, copyccs=False, signoff=None):
+    def fix_trailers(self, extras: Optional[List[LoreTrailer]] = None,
+                     copyccs: bool = False, addmysob: bool = False) -> None:
+
         config = get_main_config()
-        attpolicy = config['attestation-policy']
 
         bheaders, message, btrailers, basement, signature = LoreMessage.get_body_parts(self.body)
-        # Now we add mix-in trailers
-        trailers = btrailers + self.followup_trailers
+
+        sobtr = LoreTrailer()
+        hasmysob = False
+        if sobtr in btrailers:
+            # Our own signoff always moves to the bottom of all trailers
+            hasmysob = True
+            btrailers.remove(sobtr)
+
+        new_trailers = self.followup_trailers
+        if extras:
+            new_trailers += extras
+
+        if sobtr in new_trailers:
+            # Our own signoff always moves to the bottom of all trailers
+            new_trailers.remove(sobtr)
+            addmysob = True
 
         if copyccs:
             alldests = email.utils.getaddresses([str(x) for x in self.msg.get_all('to', [])])
@@ -1548,66 +1659,77 @@ class LoreMessage:
             alldests.sort(key=lambda x: x[1].find('@') > 0 and x[1].split('@')[1] + x[1].split('@')[0] or x[1])
             for pair in alldests:
                 found = False
-                for ftr in trailers:
-                    if ftr[1].lower().find(pair[1].lower()) >= 0:
+                for fltr in btrailers + new_trailers:
+                    if fltr.email_eq(pair[1]):
                         # already present
                         found = True
                         break
 
                 if not found:
                     if len(pair[0]):
-                        trailers.append(('Cc', f'{pair[0]} <{pair[1]}>', None, None))  # noqa
+                        altr = LoreTrailer(name='Cc', value=f'{pair[0]} <{pair[1]}>')
                     else:
-                        trailers.append(('Cc', pair[1], None, None))  # noqa
-
-        fixtrailers = list()
-        # If we received a signoff trailer:
-        # - if it's already present, we move it to the bottom
-        # - if not already present, we add it
-        new_signoff = True
-        for trailer in trailers:
-            if list(trailer[:3]) in fixtrailers:
-                # Dupe
-                continue
+                        altr = LoreTrailer(name='Cc', value=pair[1])
+                    new_trailers.append(altr)
+
+        torder = config.get('trailer-order')
+        if torder and torder != '*':
+            # this only applies to trailers within our chain of custody, so walk existing
+            # body trailers backwards and stop at the outermost Signed-off-by we find (if any)
+            for bltr in reversed(btrailers):
+                if bltr.lname == 'signed-off-by':
+                    break
+                btrailers.remove(bltr)
+                new_trailers.insert(0, bltr)
+
+            ordered_trailers = list()
+            for glob in [x.strip().lower() for x in torder.split(',')]:
+                if not len(new_trailers):
+                    break
+                for ltr in list(new_trailers):
+                    if fnmatch.fnmatch(ltr.lname, glob):
+                        ordered_trailers.append(ltr)
+                        new_trailers.remove(ltr)
+            if len(new_trailers):
+                # Tack them to the bottom
+                ordered_trailers += new_trailers
+            new_trailers = ordered_trailers
 
-            if signoff and tuple(trailer[:3]) == tuple(signoff):
-                # Skip it, we'll add it at the bottom
-                new_signoff = False
-                logger.debug('    . %s: %s', signoff[0], signoff[1])
+        attpolicy = config['attestation-policy']
+        fixtrailers = btrailers
+
+        for ltr in new_trailers:
+            if ltr in fixtrailers:
                 continue
 
-            fixtrailers.append(list(trailer[:3]))
-            if trailer[:3] not in btrailers:
-                extra = ''
-                if trailer[3] is not None:
-                    fmsg = trailer[3]
-                    for attestor in fmsg.attestors:  # noqa
-                        if attestor.passing:
-                            extra = ' (%s %s)' % (attestor.checkmark, attestor.trailer)
-                        elif attpolicy in ('hardfail', 'softfail'):
-                            extra = ' (%s %s)' % (attestor.checkmark, attestor.trailer)
-                            if attpolicy == 'hardfail':
-                                import sys
-                                logger.critical('---')
-                                logger.critical('Exiting due to attestation-policy: hardfail')
-                                sys.exit(1)
-
-                    logger.info('    + %s: %s%s', trailer[0], trailer[1], extra)
-                else:
-                    logger.debug('    . %s: %s', trailer[0], trailer[1])
+            fixtrailers.append(ltr)
+            extra = ''
+            if ltr.lmsg is not None:
+                for attestor in ltr.lmsg.attestors:
+                    if attestor.passing:
+                        extra = ' (%s %s)' % (attestor.checkmark, attestor.trailer)
+                    elif attpolicy in ('hardfail', 'softfail'):
+                        extra = ' (%s %s)' % (attestor.checkmark, attestor.trailer)
+                        if attpolicy == 'hardfail':
+                            import sys
+                            logger.critical('---')
+                            logger.critical('Exiting due to attestation-policy: hardfail')
+                            sys.exit(1)
+
+                logger.info('    + %s%s', ltr.as_string(omit_extinfo=True), extra)
 
-        if signoff:
+        if addmysob:
             # Tack on our signoff at the bottom
-            fixtrailers.append(list(signoff))
-            if new_signoff:
-                logger.info('    + %s: %s', signoff[0], signoff[1])
+            fixtrailers.append(sobtr)
+            if not hasmysob:
+                logger.info('    + %s', sobtr.as_string(omit_extinfo=True))
 
         # Reconstitute the message
         self.body = ''
         if bheaders:
-            for bheader in bheaders:
+            for bltr in bheaders:
                 # There is no [extdata] in git headers, so we ignore bheader[2]
-                self.body += '%s: %s\n' % (bheader[0], bheader[1])
+                self.body += bltr.as_string(omit_extinfo=True) + '\n'
             self.body += '\n'
 
         newmessage = ''
@@ -1617,20 +1739,18 @@ class LoreMessage:
                 newmessage += '\n'
 
         if len(fixtrailers):
-            for trailer in fixtrailers:
-                newmessage += '%s: %s\n' % (trailer[0], trailer[1])
-                if trailer[2]:
-                    newmessage += '%s\n' % trailer[2]
+            for ltr in fixtrailers:
+                newmessage += ltr.as_string() + '\n'
 
         self.message = self.subject + '\n\n' + newmessage
         self.body += newmessage
 
         if len(basement):
             self.body += '---\n'
-            self.body += basement.rstrip('\r\n') + '\n\n'
+            self.body += basement.rstrip('\r\n') + '\n'
         if len(signature):
             self.body += '-- \n'
-            self.body += signature.rstrip('\r\n') + '\n\n'
+            self.body += signature.rstrip('\r\n') + '\n'
 
     def get_am_subject(self, indicate_reroll=True):
         # Return a clean patch subject
@@ -1652,9 +1772,9 @@ class LoreMessage:
 
         return '[%s] %s' % (' '.join(parts), self.lsubject.subject)
 
-    def get_am_message(self, add_trailers=True, copyccs=False, allowbadchars=False):
+    def get_am_message(self, add_trailers=True, addmysob=False, extras=None, copyccs=False, allowbadchars=False):
         if add_trailers:
-            self.fix_trailers(copyccs=copyccs)
+            self.fix_trailers(copyccs=copyccs, addmysob=addmysob, extras=extras)
         bbody = self.body.encode()
         # Look through the body to make sure there aren't any suspicious unicode control flow chars
         # First, encode into ascii and compare for a quickie utf8 presence test
diff --git a/b4/command.py b/b4/command.py
index 7eb7700..94ba875 100644
--- a/b4/command.py
+++ b/b4/command.py
@@ -274,8 +274,6 @@ def cmd():
     sp_trl = subparsers.add_parser('trailers', help='Operate on trailers received for mailing list reviews')
     sp_trl.add_argument('-u', '--update', action='store_true', default=False,
                         help='Update branch commits with latest received trailers')
-    sp_trl.add_argument('-s', '--signoff', action='store_true', default=False,
-                        help='Add my Signed-off-by trailer, if not already present')
     sp_trl.add_argument('-S', '--sloppy-trailers', dest='sloppytrailers', action='store_true', default=False,
                         help='Apply trailers without email address match checking')
     sp_trl.add_argument('-F', '--trailers-from', dest='msgid',
diff --git a/b4/ez.py b/b4/ez.py
index 8a1b8ed..965ae6e 100644
--- a/b4/ez.py
+++ b/b4/ez.py
@@ -616,10 +616,6 @@ def update_trailers(cmdargs: argparse.Namespace) -> None:
     if 'name' not in usercfg or 'email' not in usercfg:
         logger.critical('CRITICAL: Please set your user.name and user.email')
         sys.exit(1)
-    if cmdargs.signoff:
-        signoff = ('Signed-off-by', f"{usercfg['name']} <{usercfg['email']}>", None)
-    else:
-        signoff = None
 
     ignore_commits = None
     # If we are in an b4-prep branch, we start from the beginning of the series
@@ -686,12 +682,6 @@ def update_trailers(cmdargs: argparse.Namespace) -> None:
         subject = msg.get('subject')
         by_subject[subject] = commit
         by_patchid[patchid] = commit
-        parts = b4.LoreMessage.get_body_parts(body)
-        # Force SOB update
-        if signoff and (signoff not in parts[2] or (len(signoff) > 1 and parts[2][-1] != signoff)):
-            updates[commit] = list()
-            if signoff not in parts[2]:
-                updates[commit].append(signoff)
 
     if cmdargs.msgid:
         msgid = b4.get_msgid(cmdargs)
@@ -764,11 +754,7 @@ def update_trailers(cmdargs: argparse.Namespace) -> None:
         logger.info('  %s', cmsg.subject)
         if len(newtrailers):
             cmsg.followup_trailers = newtrailers
-            if signoff in newtrailers:
-                logger.info('    + %s: %s', signoff[0], signoff[1])
-        elif signoff:
-            logger.info('    > %s: %s', signoff[0], signoff[1])
-        cmsg.fix_trailers(signoff=signoff)
+        cmsg.fix_trailers()
         fred.add(commit, cmsg.message)
     logger.info('---')
     args = fr.FilteringOptions.parse_args(['--force', '--quiet', '--refs', f'{start}..'])
@@ -1104,12 +1090,10 @@ def cmd_send(cmdargs: argparse.Namespace) -> None:
                         ccdests.append(pair)
 
         # add addresses seen in trailers
-        for trailer in trailers:
-            if '@' in trailer[1] and '<' in trailer[1]:
-                for pair in utils.getaddresses([trailer[1]]):
-                    if pair[1] not in seen:
-                        seen.add(pair[1])
-                        ccdests.append(pair)
+        for ltr in trailers:
+            if ltr.addr and ltr.addr[1] not in seen:
+                seen.add(ltr.addr[1])
+                ccdests.append(ltr.addr)
 
         excludes = b4.get_excluded_addrs()
         if cmdargs.not_me_too:
diff --git a/b4/mbox.py b/b4/mbox.py
index 9a6ea9c..c2e1555 100644
--- a/b4/mbox.py
+++ b/b4/mbox.py
@@ -121,9 +121,9 @@ def make_am(msgs, cmdargs, msgid):
             # Only check cover letter or first patch
             if not lmsg or lmsg.counter > 1:
                 continue
-            for trailer in list(lmsg.followup_trailers):
-                if trailer[0].lower() == 'obsoleted-by':
-                    lmsg.followup_trailers.remove(trailer)
+            for ltr in list(lmsg.followup_trailers):
+                if ltr.lname == 'obsoleted-by':
+                    lmsg.followup_trailers.remove(ltr)
                     if warned:
                         continue
                     logger.critical('---')
@@ -136,10 +136,10 @@ def make_am(msgs, cmdargs, msgid):
         logger.critical('---')
         logger.critical('NOTE: Some trailers were sent to the cover letter:')
         tseen = set()
-        for trailer in lser.patches[0].followup_trailers:
-            if tuple(trailer[:2]) not in tseen:
-                logger.critical('      %s: %s', trailer[0], trailer[1])
-                tseen.add(tuple(trailer[:2]))
+        for ltr in lser.patches[0].followup_trailers:
+            if ltr not in tseen:
+                logger.critical('      %s', ltr.as_string(omit_extinfo=True))
+                tseen.add(ltr)
         logger.critical('NOTE: Rerun with -t to apply them to all patches')
     if len(lser.trailer_mismatches):
         logger.critical('---')
@@ -526,9 +526,9 @@ def get_extra_series(msgs: list, direction: int = 1, wantvers: Optional[int] = N
             # Does it have an Obsoleted-by: trailer?
             rmsg = b4.LoreMessage(msg)
             trailers, mismatches = rmsg.get_trailers()
-            for tl in trailers:
-                if tl[0].lower() == 'obsoleted-by':
-                    for chunk in tl[1].split('/'):
+            for ltr in trailers:
+                if ltr.lname == 'obsoleted-by':
+                    for chunk in ltr.value.split('/'):
                         if chunk.find('@') > 0 and chunk not in seen_msgids:
                             obsoleted.append(chunk)
                             break
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()