Sean [off-list ref] writes:
I would argue that you shouldn't try to have it both ways.
You cannot have it both ways as-is, but this is solvable. The
invocation of am from rebase needs an extra (internal to
implementation) option to use the code it patches, and the
regular am can fold what are found on Subject: lines it used
to.
The patch as-is breaks the more important case of e-mail
acceptance codepath, because MUAs are free to fold the Subject:
line when the original line is long, and what the user (the
original patch submitter) expects to happen is that a
single-line-ness of the original Subject: of the message to be
kept. The patch breaks such a line at the place MUA happens to
fold such a long, single line, for comforming messages.