Special remote programs that use GETCONFIG/SETCONFIG are recommended
to implement it.
The description is not yet used, but will be useful later when adding a way
to make initremote list all accepted configs.
configParser now takes a RemoteConfig parameter. Normally, that's not
needed, because configParser returns a parter, it does not parse it
itself. But, it's needed to look at externaltype and work out what
external remote program to run for LISTCONFIGS.
Note that, while externalUUID is changed to a Maybe UUID, checkExportSupported
used to use NoUUID. The code that now checks for Nothing used to behave
in some undefined way if the external program made requests that
triggered it.
Also, note that in externalSetup, once it generates external,
it parses the RemoteConfig strictly. That generates a
ParsedRemoteConfig, which is thrown away. The reason it's ok to throw
that away, is that, if the strict parse succeeded, the result must be
the same as the earlier, lenient parse.
initremote of an external special remote now runs the program three
times. First for LISTCONFIGS, then EXPORTSUPPORTED, and again
LISTCONFIGS+INITREMOTE. It would not be hard to eliminate at least
one of those, and it should be possible to only run the program once.
Needed so Remote.External can query the external program for its
configs. When the external program does not support the query,
the passthrough option will make all input fields be available.
Remote now contains a ParsedRemoteConfig. The parsing happens when the
Remote is constructed, rather than when individual configs are used.
This is more efficient, and it lets initremote/enableremote
reject configs that have unknown fields or unparsable values.
It also allows for improved type safety, as shown in
Remote.Helper.Encryptable where things that used to match on string
configs now match on data types.
This is a work in progress, it does not build yet.
The main risk in this conversion is forgetting to add a field to
RemoteConfigParser. That will prevent using that field with
initremote/enableremote, and will prevent remotes that already are set
up from seeing that configuration. So will need to check carefully that
every field that getRemoteConfigValue is called on has been added to
RemoteConfigParser.
(One such case I need to remember is that credPairRemoteField needs to be
included in the RemoteConfigParser.)
