Handle mailman message/rfc822 encapsulationHEADmaster

To work around DMARC rejection rules, mailman may encapsulate the
original message in a message/rfc822 part. Support this.

Signed-off-by: Laurent Pinchart <laurent.pinchart@ideasonboard.com>

1 files changed, 19 insertions, 8 deletions

diff --git a/patch-save.py b/patch-save.py
index a9b9a3c..8508d22 100755
--- a/patch-save.py
+++ b/patch-save.py
@@ -51,14 +51,25 @@ def main(argv):
     parser = email.parser.BytesParser(policy=email.policy.default)
     msg = parser.parse(sys.stdin.buffer)
 
-    # mailman can mangle the From header to work around DMARC rejection rules.
-    # It then formats From as "Name via mailing-list <mailing-list@domain>" and
-    # stores the original sender in the Reply-to header. Restore the original
-    # author in the From header to please git-am.
-    from_header = msg.get('From')
-    reply_to = msg.get('Reply-to')
-    if reply_to and ' via ' in from_header:
-        msg.replace_header('From', reply_to)
+    # Handle mailman message mangling used to work around DMARC rejection rules:
+    #
+    # - mailman may encapsulate original messages in a message/rfc822 part.
+    #   That's an easy case, simply extract the encapsulated message. Any
+    #   additional mangling of the outer message (such as From header mangling)
+    #   can be ignored.
+    #
+    # - mailman may mangle the From header. It then formats From as "Name via
+    #   mailing-list <mailing-list@domain>" and stores the original sender in
+    #   the Reply-to header. Restore the original author in the From header to
+    #   please git-am.
+
+    if msg.get_content_type() == 'message/rfc822':
+        msg = next(msg.iter_parts())
+    else:
+        from_header = msg.get('From')
+        reply_to = msg.get('Reply-to')
+        if reply_to and ' via ' in from_header:
+            msg.replace_header('From', reply_to)
 
     subject = msg.get('Subject')
     if not subject: