In the future Xapian will apparently support this more conveniently
for the cases other than READ_ONLY => READ_ONLY
Conceptually this function seems to fit better in lib/open.cc;
database.cc is still large enough that moving the function makes
sense.
This will allow re-opening in a different mode (read/write
vs. read-only) with current Xapian API. It will also prove useful when
updating the compact functions to support more flexible database
location.
This will allow client code to provide more meaningful diagnostics. In
particular it will enable "notmuch new" to continue suggsting the user
run "notmuch setup" to create a config after "notmuch new" is
transitioned to the new configuration framework.
Fill in the remainder of the documented functionality for
n_d_open_with_config with respect to config file location. Similar
searching default locations of the database file still needs to be
added.
The main goal is to allow configuration information to be temporarily
overridden by a separate config file. That will require further
changes not in this commit.
The performance impact is unclear, and will depend on the balance
between number of queries and number of distinct metadata items read
on the first call to n_d_get_config.
