Bug#649679: [copyright-format] Clarify what distinguishes files and stand-alone license paragraphs.

[Jakub Wilk <jwilk@debian.org>]

* Charles Plessy <plessy@debian.org>, 2011-12-19, 10:12:
> Of course, I agree that making a stand-alone License paragraph with an 
> extra Fiels field would be an horror. But I am inclined to think that 
> it is obvious enough that we do not need to constrain the syntax. With 
> the change you propose extra checks are needed while parsing.

I thought it was obvious when I implemented lintian checks, but it 
turns out to not be so easy after all.

The problem is with paragraphs like this:
| Copyright: 2042, J. Random Hacker
| License: BSD-6-clauses
|  Redistribution and use in source and binary forms, with or without
|  modification, are permitted provided that the following conditions
|  are met: blah, blah, blah, blah, blah and blah.

In early DEP-5 drafts, Files field could be ommited in certain 
circumstances, so this could have been a perfectly valid files 
paragraph. But with the current DEP-5 version, if we allow any extra 
fields, this suddenly becomes a valid stand-alone license paragraph.

Please see bug #652380 for a real-world example.

--
Jakub Wilk