[9fans] diff to get a /dev/config file

[Fco.J.Ballesteros <nemo@plan9.escet.urjc.es>]

For those like me who just don't remember what was in the config file
used to build the kernel, this adds /dev/config (#c/config).
/dev/config holds a copy of the config file used to build the kernel.
If you are interested, instructions follow.

At /sys/src/9/port/portmkfile, replace the $CONF.c rule with this one:

$CONF.c:	../port/mkdevc $CONF
	rc ../port/mkdevc $CONF > $CONF.c
	{echo 'uchar configfile[]={'
	 xd -1x $CONF |
		sed -e 's/^[0-9a-f]+ //' -e 's/ ([0-9a-f][0-9a-f])/0x\1,/g'
	 echo 0,
	 echo '};'} >> $CONF.c

Then apply this change:
diff devcons.c /sys/src/9/port/devcons.c
500a501
> 	Qconfig,
530a532
> 	"config",	{Qconfig},	0,	0444,
653a656
> 	extern char configfile[];
758c761,762
<
---
> 	case Qconfig:
> 		return readstr((ulong)offset, buf, n, configfile);

If you applied it, you may also like to apply this to /sys/man/3/cons:
diff cons /sys/man/3/cons
28a29
> .B /dev/config
146a148,151
> .PP
> The
> .B config
> file contains a copy of the kernel configuration file used to build the kernel.

enjoy