-Fix notmuch.c to call add_timestamp/get_timestampt with path names
-relative to the database path. (Otherwise, moving the database to a
-new directory will result in notmuch creating new timestamp documents
-and leaving stale ones behind.)
-
-Fix notmuch.c to use a DIR prefix for directory timestamps, (the idea
-being that it can then add other non-directory timestamps such as for
-noting how far back in the past mail has been indexed, and whether it
-needs to re-tag messages based on a theoretical "auto-tags"
-configuration file).
-