By using an enum we can have better error detection than copy pasting
key strings around.
The question of what layer this belongs in is a bit
tricky. Historically most of the keys are defined by the CLI. On the
other hand features like excludes are supported in the
library/bindings, and it makes sense to configure them from the
library as well.
The somewhat long prefix for notmuch_config_t is to avoid collisions
with the existing usage in notmuch-client.h.
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 trick of having a common header file doesn't work to share between
test scripts, so make an include file in the test directory.
The use of #include <notmuch-test.h> looks slightly pretentious, but
the include file is not actually in the current (temporary) directory.
Since xapian provides the ability to restrict the iterator to a given
prefix, we expose this ability to the user. Otherwise we mimic the other
iterator interfances in notmuch (e.g. tags.c).
This is a thin wrapper around the Xapian metadata API. The job of this
layer is to keep the config key value pairs from colliding with other
metadata by transparently prefixing the keys, along with the usual glue
to provide a C interface.
The split of _get_config into two functions is to allow returning of the
return value with different memory ownership semantics.
