during some maintenance work today, bremner and i noticed that message
delivery via "notmuch insert" creates files that are stricter than the
umask.

using notmuch 0.23.6, with umask 027, "notmuch insert" created files
with mode 0600.  i would have expected 0640.

using strace, i don't see notmuch invoking any system calls to umask()
or chmod() so i'm not sure how these permissions are getting set in the
first place.

is there a reason that "notmuch insert" should be stricter than the
umask?  does this ring any bells for people?

        --dkg