Please read the docs and sample code (I suggest gpa and gpgme). GOT_IT
indicates that a line has been received in response to a GET_xxx status.

I could not easily figure out what I was supposed to infer from the source code
of gpa or gpgme, but after playing about with it, I suppose I can detect the
error by noticing that the next GET_LINE issues a keyedit.prompt rather than
continuing with the workflow. This means I will have to write some state-keeping
logic instead of merely switching on the GET_LINE, and all users of this
interface will need to implement a similar thing.

To reduce the complexity for scripters here, might I suggest adding an extra
parameter to GOT_IT to explicitly communicate to the client script about any
errors? At least from the gpa/gpgme code it seems there is a generic parser that
can cope with extra parameters to any status line.

If anyone is affected by this (I don't know of others using this interface),
they can easily rewrite their parsing code to cope with both the old and new
GOT_IT lines (with or without a parameter).

BTW, this is the sort of thing that documentation would be helpful for.