Allow breaking threads using --no-parent

It is a common request to be able to get a partial thread in case
someone submitted an auxiliary standalone patch in the middle of a
larger patch series. Passing the msgid of the start of the thread along
with --no-parent should tell b4 to break the thread at the start of the
message-id specified and only consider that message and its children.

Suggested-by: Mark Brown <broonie@kernel.org>
Link: https://lore.kernel.org/tools/YpTI9lhCfA7shi6j@sirena.org.uk/
Signed-off-by: Konstantin Ryabitsev <konstantin@linuxfoundation.org>

3 files changed, 24 insertions, 9 deletions

diff --git a/b4/__init__.py b/b4/__init__.py
index 1ac7eb1..bc4dd36 100644
--- a/b4/__init__.py
+++ b/b4/__init__.py
@@ -2148,8 +2148,9 @@ def get_msgid(cmdargs) -> Optional[str]:
     return msgid
 
 
-def get_strict_thread(msgs, msgid):
+def get_strict_thread(msgs, msgid, noparent=False):
     want = {msgid}
+    ignore = set()
     got = set()
     seen = set()
     maybe = dict()
@@ -2157,6 +2158,8 @@ def get_strict_thread(msgs, msgid):
     while True:
         for msg in msgs:
             c_msgid = LoreMessage.get_clean_msgid(msg)
+            if c_msgid in ignore:
+                continue
             seen.add(c_msgid)
             if c_msgid in got:
                 continue
@@ -2168,7 +2171,16 @@ def get_strict_thread(msgs, msgid):
                 msgrefs += email.utils.getaddresses([str(x) for x in msg.get_all('in-reply-to', [])])
             if msg.get('References', None):
                 msgrefs += email.utils.getaddresses([str(x) for x in msg.get_all('references', [])])
+            # If noparent is set, we pretend the message we got passed has no references, and add all
+            # parent references of this message to ignore
+            if noparent and msgid == c_msgid:
+                logger.info('Breaking thread to remove parents of %s', msgid)
+                ignore = set([x[1] for x in msgrefs])
+                msgrefs = list()
+
             for ref in set([x[1] for x in msgrefs]):
+                if ref in ignore:
+                    continue
                 if ref in got or ref in want:
                     want.add(c_msgid)
                 elif len(ref):
@@ -2206,7 +2218,7 @@ def get_strict_thread(msgs, msgid):
         return None
 
     if len(msgs) > len(strict):
-        logger.debug('Reduced mbox to strict matches only (%s->%s)', len(msgs), len(strict))
+        logger.debug('Reduced thread to requested matches only (%s->%s)', len(msgs), len(strict))
 
     return strict
 
@@ -2266,7 +2278,8 @@ def get_pi_thread_by_url(t_mbx_url, nocache=False):
     return list(deduped.values())
 
 
-def get_pi_thread_by_msgid(msgid, useproject=None, nocache=False, onlymsgids: Optional[set] = None):
+def get_pi_thread_by_msgid(msgid: str, useproject: Optional[str] = None, nocache: bool = False,
+                           onlymsgids: Optional[set] = None) -> Optional[list]:
     qmsgid = urllib.parse.quote_plus(msgid)
     config = get_main_config()
     loc = urllib.parse.urlparse(config['midmask'])
diff --git a/b4/command.py b/b4/command.py
index 6d3c899..aa307da 100644
--- a/b4/command.py
+++ b/b4/command.py
@@ -55,6 +55,8 @@ def cmd_am_common_opts(sp):
                          '"-P *globbing*" to match on commit subject)')
     sp.add_argument('--cc-trailers', dest='copyccs', action='store_true', default=False,
                     help='Copy all Cc\'d addresses into Cc: trailers')
+    sp.add_argument('--no-parent', dest='noparent', action='store_true', default=False,
+                    help='Break thread at the msgid specified and ignore any parent messages')
     sp.add_argument('--allow-unicode-control-chars', dest='allowbadchars', action='store_true', default=False,
                     help='Allow unicode control characters (very rarely legitimate)')
 
diff --git a/b4/mbox.py b/b4/mbox.py
index c2e6319..4ac2c29 100644
--- a/b4/mbox.py
+++ b/b4/mbox.py
@@ -656,12 +656,9 @@ def get_msgs(cmdargs) -> Tuple[Optional[str], Optional[list]]:
             sys.exit(1)
 
         pickings = set()
-        try:
-            if cmdargs.cherrypick == '_':
-                # Just that msgid, please
-                pickings = {msgid}
-        except AttributeError:
-            pass
+        if 'cherrypick' in cmdargs and cmdargs.cherrypick == '_':
+            # Just that msgid, please
+            pickings = {msgid}
         msgs = b4.get_pi_thread_by_msgid(msgid, useproject=cmdargs.useproject, nocache=cmdargs.nocache,
                                          onlymsgids=pickings)
         if not msgs:
@@ -693,6 +690,9 @@ def get_msgs(cmdargs) -> Tuple[Optional[str], Optional[list]]:
             logger.critical('Mailbox %s does not exist', cmdargs.localmbox)
             sys.exit(1)
 
+    if msgid and 'noparent' in cmdargs and cmdargs.noparent:
+        msgs = b4.get_strict_thread(msgs, msgid, noparent=True)
+
     if not msgid and msgs:
         for msg in msgs:
             msgid = msg.get('Message-ID', None)