This unifies the 3 methods of reading config
* command line
* environment variable
* config file
And allows them all to be configured in all places. This is done by
making the []fs.Option in the backend registration be the master
source of what the backend options are.
The backend changes are:
* Use the new configmap.Mapper parameter
* Use configstruct to parse it into an Options struct
* Add all config to []fs.Option including defaults and help
* Remove all uses of pflag
* Remove all uses of config.FileGet
This allows the backend to pass a errorHandler function to the doConfig
function. The webserver will pass the current request as a parameter to
the function.
The function can then examine all paramters and build the AuthError
struct which contains name, code, description of the error. A link to
the docs can be added to the HelpURL field.
oauthutil then takes care of formatting for the HTML response page. The
error details are also returned as an error in the server.err channel
and will be logged to the commandline.
The purpose of this is to make it easier to maintain and eventually to
allow the rclone backends to be re-used in other projects without
having to use the rclone configuration system.
The new code layout is documented in CONTRIBUTING.
