Weird behaviour in notmuch new

[Mark Walters <markwalters1009@gmail.com>]

Hi

I was experimenting with letting notmuch new take an argument to tell it
to scan only a particular directory (and sub-directories) for new
messages. I came across the following strange behaviour which is also
present in master (with a fresh database)

I have a bunch of maildirs in /home/mail: so folders .mail.foo/
.mail.bar/ each of which has cur/new/tmp and all the messages are in
cur.

If I do mv .mail.foo .mail.bar/ and run notmuch new I get the expected
lots of renames (900 or so in the case I was trying). But if I then do
mv .mail.bar/.mail.foo . and run notmuch new almost all the messages get
removed (but 30 renames do get detected). If I then do touch .mail.foo/*
the messages get found again

I am guessing the 30 renames might be because those 30 have duplicates
somewhere else. 

But the other behaviour has me puzzled.

Best wishes

Mark