cmd/revid-cli: input file is closed before we can read it

[Saxon Milton]

if we do file output, we are getting an error indicating that the file has been closed when we're trying to read from it. This is because in setupInputForFile we do a defer on f.Close() but before the return we run lexTo as a routine which requires the file.

I propose that we have revid possess a File type and close in revid.Stop().

[kortschak]

I don't think a file type is needed. There are two options, having an interface input that's the cognate of the loadSenders or have the startup routines return a closure, func() error, that handles resource freeing (in this case closing the file).

[Saxon Milton]

Resolved in PR #194