This is effectively a revert of
commit 6812136bf5
Author: Jani Nikula <jani@nikula.org>
Date: Mon Mar 31 00:21:48 2014 +0300
lib: drop support for single-message mbox files
The intention was to drop support for indexing new single-message mbox
files (and whether that was a good idea in the first place is
arguable). However this inadvertently broke support for reading
headers from previously indexed single-message mbox files, which is
far worse.
Distinguishing between the two cases would require more code than
simply bringing back support for single-message mbox files.
We've supported mbox files containing a single message for historical
reasons, but the support has been deprecated, with a warning message
while indexing, since Notmuch 0.15. Finally drop the support, and
consider all mbox files non-email.
All test scripts to be executed are now named as T\d\d\d-name.sh,
numers in increments of 10.
This eases adding new tests and developers to see which are test scripts
that are executed by test suite and in which order.
