[PATCH b4] ez: avoid duplicate signatures on resend

'b4 send --resend' rebuilds messages from the historical sent tag and
appends the current email signature to the cover text. If the stored
cover already ends in a signature block, the regenerated resend can carry
two footer blocks, as we can see here[1].

Strip an existing trailing cover signature before adding the current one.
Recognize both the standard "-- " delimiter and the bare "--" delimiter
observed in archived mail.

[1] https://lore.kernel.org/all/20260511-alsa-hda-cs35l41-fw-work-teardown-v1-1-1184e9bc4f25@gmail.com/

Signed-off-by: Cássio Gabriel <[email protected]>
---
 src/b4/ez.py         | 15 +++++++++++----
 src/tests/test_ez.py | 21 +++++++++++++++++++++
 2 files changed, 32 insertions(+), 4 deletions(-)

diff --git a/src/b4/ez.py b/src/b4/ez.py
index 3e81138..4f55f0f 100644
--- a/src/b4/ez.py
+++ b/src/b4/ez.py
@@ -1734,6 +1734,15 @@ def get_cover_subject_body(cover: str) -> Tuple[b4.LoreSubject, str]:
     return lsubject, cbody
 
 
+def strip_cover_signature(cbody: str) -> str:
+    body = cbody.replace('\r', '').rstrip('\n')
+    sigpos = max(body.rfind('\n-- \n'), body.rfind('\n--\n'))
+    if sigpos >= 0:
+        return body[:sigpos].rstrip('\n')
+
+    return body
+
+
 def rethread(patches: List[Tuple[str, EmailMessage]]) -> None:
     refto = patches[0][1].get('message-id')
     if refto is not None:
@@ -1992,7 +2001,7 @@ def get_sent_tag_as_patches(
     cover, base_commit, change_id = get_base_changeid_from_tag(tagname)
 
     csubject, cbody = get_cover_subject_body(cover)
-    cbody = cbody.strip() + '\n-- \n' + b4.get_email_signature()
+    cbody = strip_cover_signature(cbody) + '\n-- \n' + b4.get_email_signature()
     prefixes = ['RESEND'] + csubject.get_extra_prefixes(exclude=['RESEND'])
     msgid_tpt = make_msgid_tpt(change_id, revision)
     seriests = int(time.time())
@@ -2659,9 +2668,7 @@ def reroll(
     mybranch: str, tag_msg: str, msgid: str, tagprefix: str = SENT_TAG_PREFIX
 ) -> None:
     # Remove signature
-    chunks = tag_msg.rsplit('\n-- \n')
-    if len(chunks) > 1:
-        tag_msg = chunks[0] + '\n'
+    tag_msg = strip_cover_signature(tag_msg) + '\n'
 
     cover, tracking = load_cover(strip_comments=True)
     revision = tracking['series']['revision']
diff --git a/src/tests/test_ez.py b/src/tests/test_ez.py
index 3d05ef9..5abfea2 100644
--- a/src/tests/test_ez.py
+++ b/src/tests/test_ez.py
@@ -408,3 +408,24 @@ def test_store_cover_preserves_series_notes(prepdir_commit: str) -> None:
     ecode, backup_oid = b4.git_run_command(None, ['rev-parse', f'refs/original/{cb}'])
     assert ecode == 0
     assert backup_oid.strip() == pre_head
+
+
[email protected]('sigmarker', ['-- ', '--'])
+def test_strip_cover_signature(sigmarker: str) -> None:
+    cbody = (
+        'Cover text.\n\n'
+        '---\n'
+        'base-commit: abc123\n'
+        'change-id: 20260101-test-change-id\n\n'
+        'Best regards,\n'
+        f'{sigmarker}\n'
+        'Test User <[email protected]>\n'
+    )
+
+    assert b4.ez.strip_cover_signature(cbody) == (
+        'Cover text.\n\n'
+        '---\n'
+        'base-commit: abc123\n'
+        'change-id: 20260101-test-change-id\n\n'
+        'Best regards,'
+    )

---
base-commit: d5d981426ead3f490713ef5d2fd1aa3d0f13b005
change-id: 20260525-resend-signature-fix-9ef453adc559

Best regards,
--  
Cássio Gabriel <[email protected]>