[9fans] file heuristics on troff input

[Pietro Gagliardi <pietro10@mac.com>]

Just a bit of humor:

	COMPUTER								ME
	% cd troff
	% file *
	advp9prog:				directory			yes (old attempt at plan 9 programmer's
guide)
	algoawk:				directory			yes (awk book)
	bentley.ms:				troff -ms input	yes (Bentley paper)
	bentley2.ms:				Ascii text		wtf? (Bentley paper retry)
	cod.ms:					troff input		why not -ms? (paper on calculator program
I'm writing)
	cod.ms.part:				Ascii			file doesn't understand .ig and pic? (part of
cod.ms that doesn't belong yet)
	forloop.ms:				Ascii			this is pic input (flowchart on how for loops
work in JavaScript)
	jstut.ms:					HTML file		very wrong (JavaScript tutorial)
	luxidejavu.ms:			troff input		fine (ripped from p9port, -ms .FP with
DejaVu and Luxi Sans)
	programming.ms:			c program		no one would dare put a program that big
into one file, stupid (new attempt at programming tutorial, you'll see
it when it's done)
	school:					directory			good (stuff for school)
	% file advp9prog/*
	adv9prog/ch1:			Ascii			wtf?
	adv9prog/ch2:			c program		not again
	adv9prog/dates:			short Ascii		all right (I date evereything for
record keeping purposes)
	adv9prog/mkfile:			short Ascii		don't you know about mk?
	% file algoawk/*
	algoawk/book_macros:	Ascii			?
	algoawk/ch1:			Ascii text		oh my gawd, something different!
	algoawk/colophon:		Ascii			...
	algoawk/dates:			short Ascii		good
	algoawk/intro:			Ascii			no
	algoawk/mkfile:			Ascii			still no mk...
	algoawk/show:			rc executable file	right
	% file school/*
	...										To save you the trouble, they're either directories or -
ms input, but either showing "directory" or "Ascii."

A full report of my troff directory and subdirectories is in /n/
sources/contrib/pietro/file.funny.

So that's only one file that is absolutely correct. It turns out that
the problem is file isn't reading the

	.FP font

as a troff -ms macro line. In the books, they don't read enough lines
to see that there are more .PPs than there are #includes. Ah well.

And if you thought that was funny, look at the example of a file that
actually seeks to more than one line from UNIX in "The UNIX-HATERS
Handbook" (now a free PDF from its authors).