diffy: new command
 [rsc] --rwxrwxr-x M 1635703 rsc sys 277 Feb 23 06:41 rc/bin/diffy
 [rsc] --rw-rw-r-- M 1635703 glenda sys 2607 Feb 23 06:41 sys/man/1/yesterday
	/n/sourcesdump/2006/0223/plan9/sys/man/1/yesterday:1,6 - 
	/n/sourcesdump/2006/0224/plan9/sys/man/1/yesterday:1,6
	  .TH YESTERDAY 1
	  .SH NAME
	- yesterday \- print file names from the dump
	+ yesterday, diffy \- print file names from the dump
	  .SH SYNOPSIS
	  .B yesterday
	  [
	/n/sourcesdump/2006/0223/plan9/sys/man/1/yesterday:12,17 - 
	/n/sourcesdump/2006/0224/plan9/sys/man/1/yesterday:12,23
	  .I \-date
	  ]
	  .I files ...
	+ .PP
	+ .I diffy
	+ [
	+ .B -abcefmnrw
	+ ]
	+ .I files ...
	  .SH DESCRIPTION
	  .I Yesterday
	  prints the names of the
	/n/sourcesdump/2006/0223/plan9/sys/man/1/yesterday:98,103 - 
	/n/sourcesdump/2006/0224/plan9/sys/man/1/yesterday:104,116
	  .PP
	  .I Yesterday
	  does not guarantee that the string it prints represents an existing file.
	+ .PP
	+ .I Diffy
	+ runs
	+ .IR diff (1)
	+ with the given options
	+ to compare yesterday's version of each of the named files
	+ with today's.
	  .SH EXAMPLES
	  .PP
	  Back up to yesterday's MIPS binary of
	/n/sourcesdump/2006/0223/plan9/sys/man/1/yesterday:121,126 - 
	/n/sourcesdump/2006/0224/plan9/sys/man/1/yesterday:134,145
	  .IP
	  .EX
	  yesterday -d -0301 /sys/src/libc/port/*.c
	+ .EE
	+ .PP
	+ Find what has changed in the source tree today:
	+ .IP
	+ .EX
	+ diffy -r /sys/src
	  .EE
	  .SH FILES
	  .B /n/dump