Commits or checkouts that modify a large fraction of the messages in
the database should be relatively rare (and in some automated process,
probably non-existent). For initial setup, where such operations are
expected, the user can pass --force.
This is probably more convenient than always passing a command line
argument.
Use notmuch-config for consistency with other notmuch CLI tools.
Now that there is something relevant in the config files, test the
--config option.
The previous defaults were not suitable for personal (i.e. not
bugtracking for notmuch development) use.
Provide two ways for the user to select nmbug compatible defaults;
command line argument and checking the name of the script.
