All the time I thought what makes "notmuch new" so abysmally slow is the
stat() for each maildir. But as it continued to be slow even after I
moved most mails out of 'new' (into 'new-20120624'), I strace'd notmuch
and noticed it listed even unchanged directories, thereby listing and
iterating over each and every single of the 900k mails in my mail store.

There's still quite some room for further improvements as it continues
to take several minutes to scan < 100 new mails in changed directories
containing < 1000 mails in total. Even the rsync run that fetches the
new mails is faster.

Sascha Silbe (3):
  lib: fix NULL checks for filenames iterators
  lib: add support for rewinding a filenames iterator
  new: don't read unchanged directories from disk

 lib/filenames.c |   15 ++++++-
 lib/notmuch.h   |    8 ++++
 notmuch-new.c   |  130 +++++++++++++++++++++++++++++++++++++++++--------------
 3 files changed, 119 insertions(+), 34 deletions(-)

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1.7.10