argument parsing refactoring round3

[David Bremner]

David Bremner <david at tethera.net> writes:

> guyzmo <guyzmo+notmuch at m0g.net> writes:
>
>> I was wondering whether you had considered actually using `docopt` to
>> generate the CLI parser from the output.

> As it stands, I'm not particularly annoyed with the notmuch argument
> parsing code, so I mainly see negative issues about your proposal.

On the other hand, I do find the config handling code annoying, so if
people have some ideas about that, I am interested to hear them.  There
is now almost 1000 lines of C in notmuch-config.c, and despite some
efforts to streamline things, there is a lot of copying and pasting
every time someone wants to add a configuration option.

d