[PATCH b4 1/2] Fix basement detection for empty commit message bodies

["Kyle Meyer" <kyle@kyleam.com>]

The get_body_parts() method added in ba6c790 (Parse body parts into
usual chunks, 2020-04-27) splits the commit message body on "\n---\n"
and takes the second half as the "basement" of the patch.  The body is
stripped of flanking new lines, though, so a delimiter beginning with
a new line isn't appropriate for commit messages without a message
body.  Make the starting new line optional.

Note that this doesn't matter in the end in terms of the final applied
patch.  Before 31f33fd (Fix body part parsing when '---' is not used,
2020-06-08), the expected patch output was produced despite the diff
lines being processed as the message body.  After that commit, the
information following the triple dash is a bit off, but it doesn't
matter because git discards it anyway.

Signed-off-by: Kyle Meyer <kyle@kyleam.com>
---
 b4/__init__.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/b4/__init__.py b/b4/__init__.py
index de6a274..7e3134f 100644
--- a/b4/__init__.py
+++ b/b4/__init__.py
@@ -1204,7 +1204,7 @@ def get_body_parts(body):
             signature = sparts[1]
             body = sparts[0].rstrip('\n')
 
-        parts = body.split('\n---\n', 1)
+        parts = re.split('^---\n', body, maxsplit=1, flags=re.M)
         if len(parts) == 2:
             basement = parts[1].rstrip('\n')
         elif body.find('\ndiff ') >= 0:
-- 
2.27.0