[RFC,5/6] patchtest: allow malformed Mbox

diff --git a/meta/lib/patchtest/mbox.py b/meta/lib/patchtest/mbox.py
index 1d95819b7aee5daa879eac0710827b45b2acfec3..640e74001490ba6a6234da4acf1b13094c280d37 100644
--- a/meta/lib/patchtest/mbox.py
+++ b/meta/lib/patchtest/mbox.py
@@ -15,9 +15,10 @@  import re
 
 # From: https://stackoverflow.com/questions/59681461/read-a-big-mbox-file-with-python
 class MboxReader:
-    def __init__(self, filepath):
+    def __init__(self, filepath, allow_malformed=False):
         self.handle = open(filepath, 'rb')
-        assert self.handle.readline().startswith(b'From ')
+        if not allow_malformed:
+            assert self.handle.readline().startswith(b'From ')
 
     def __enter__(self):
         return self
@@ -51,8 +52,8 @@  class Patch:
         self.diff = self.split_body[1]
 
 class PatchSeries:
-    def __init__(self, filepath):
-        with MboxReader(filepath) as mbox:
+    def __init__(self, filepath, allow_malformed=False):
+        with MboxReader(filepath, allow_malformed=allow_malformed) as mbox:
             self.patches = [Patch(message) for message in mbox]
 
         assert self.patches
diff --git a/meta/lib/patchtest/repo.py b/meta/lib/patchtest/repo.py
index 8ec8f68a0bc61fc3b52b5d965663fa3bcfc0a684..9df50ef65f6a2fabc5ff7c5c06252ff44b2e6e9b 100644
--- a/meta/lib/patchtest/repo.py
+++ b/meta/lib/patchtest/repo.py
@@ -17,10 +17,10 @@  class PatchTestRepo(object):
     # prefixes used for temporal branches/stashes
     prefix = 'patchtest'
 
-    def __init__(self, patch, repodir, commit=None, branch=None):
+    def __init__(self, patch, repodir, commit=None, branch=None, allow_malformed=False):
         self.repodir = repodir
         self.repo = git.Repo.init(repodir)
-        self.patch = mbox.PatchSeries(patch)
+        self.patch = mbox.PatchSeries(patch, allow_malformed=allow_malformed)
         self.current_branch = self.repo.active_branch.name
 
         # targeted branch defined on the patch may be invalid, so make sure there
diff --git a/scripts/patchtest b/scripts/patchtest
index 82ce665c1a5c950dfaf02cda9ed70b935a9bfe25..2b0bda88cabec3812499f88bb3c4b68d7352bff0 100755
--- a/scripts/patchtest
+++ b/scripts/patchtest
@@ -33,7 +33,7 @@  logger.setLevel(logging.INFO)
 info = logger.info
 error = logger.error
 
-def getResult(patch, mergepatch, logfile=None):
+def getResult(patch, mergepatch, logfile=None, allow_malformed=False):
 
     class PatchTestResult(unittest.TextTestResult):
         """ Patchtest TextTestResult """
@@ -51,6 +51,7 @@  def getResult(patch, mergepatch, logfile=None):
                 "commit": PatchtestParser.basecommit,
                 "branch": PatchtestParser.basebranch,
                 "patch": patch,
+                "allow_malformed": allow_malformed,
             }
 
             self.repo_error    = False
@@ -152,17 +153,17 @@  def _runner(resultklass, prefix=None):
 
     return 0
 
-def run(patch, logfile=None):
+def run(patch, logfile=None, allow_malformed=False):
     """ Load, setup and run pre and post-merge tests """
     # Get the result class and install the control-c handler
     unittest.installHandler()
 
     # run pre-merge tests, meaning those methods with 'pretest' as prefix
-    premerge_resultklass = getResult(patch, False, logfile)
+    premerge_resultklass = getResult(patch, False, logfile, allow_malformed)
     premerge_result = _runner(premerge_resultklass, 'pretest')
 
     # run post-merge tests, meaning those methods with 'test' as prefix
-    postmerge_resultklass = getResult(patch, True, logfile)
+    postmerge_resultklass = getResult(patch, True, logfile, allow_malformed)
     postmerge_result = _runner(postmerge_resultklass, 'test')
 
     if not PatchtestParser.no_summary:
@@ -207,6 +208,7 @@  def main():
         patch_list = [patch_path]
 
     for patch in patch_list:
+        allow_malformed = False
         if patch == "-":
             import tempfile
 
@@ -216,6 +218,9 @@  def main():
             logger.info('Testing patch from stdin')
             tmp_patch = True
             patch = patch.name
+            # b4 strips the "From ", c.f.
+            # https://git.kernel.org/pub/scm/utils/b4/b4.git/tree/src/b4/__init__.py?h=stable-0.14.y#n3494
+            allow_malformed = True
         elif os.path.getsize(patch) == 0:
             logger.error('patchtest: patch is empty')
             return 1
@@ -229,9 +234,9 @@  def main():
 
         try:
             if log_path:
-                run(patch, log_path)
+                run(patch, log_path, allow_malformed=allow_malformed)
             else:
-                run(patch)
+                run(patch, allow_malformed=allow_malformed)
         finally:
             if tmp_patch:
                 os.remove(patch)