add dirdiff(1)

Reference: /n/atom/patch/applied/dirdiff
Date: Thu Mar 12 17:38:25 CET 2015
Signed-off-by: quanstro@quanstro.net

--- /rc/bin/dirdiff	Thu Jan  1 00:00:00 1970
+++ /rc/bin/dirdiff	Thu Mar 12 17:38:09 2015
@@ -0,0 +1,48 @@
+#!/bin/rc
+
+# 
+# treat lists as sets
+# ∩cl is A\B union B\A
+# listminus is the set relative complement A \ B)
+
+fn ∩ {echo $$1 $$2 | sed 's/ /\n/g' | sort | uniq -d}
+fn not∩ {echo $$1 $$2 | sed 's/ /\n/g' | sort | uniq -u}
+fn listminus {c=`{∩ $1 $2} not∩ c $1}
+
+flagfmt='a,d'
+args='[old [new]]'
+if(! eval `''{aux/getflags $*}){
+	aux/usage
+	exit usage
+}
+switch($#*){
+case 2
+	old=$1
+	new=$2
+case 1
+	old=$1
+	new=`{yesterday $1}
+case 0
+	old=.
+	new=`{yesterday .}
+case *
+	aux/usage
+	exit usage
+}
+
+#  directory differences
+new=`{cd $new && echo *}
+old=`{cd $old && echo *}
+
+switch($#flaga ^ $#flagd){
+case 11
+	echo 'added=('  `{listminus old new} ')'
+	echo 'deleted=('  `{listminus new old} ')'
+case 10
+	echo `{listminus old new}
+case 01
+	echo  `{listminus new old}
+case 00
+	echo 'added=('  `{listminus old new} ')'
+	echo 'deleted=('  `{listminus new old} ')'
+}
--- /sys/man/1/dirdiff	Thu Jan  1 00:00:00 1970
+++ /sys/man/1/dirdiff	Thu Mar 12 17:38:10 2015
@@ -0,0 +1,48 @@
+.TH DIRDIFF 1
+.SH NAME
+dirdiff \- directory file differences
+.SH SYNOPSIS
+.B dirdiff
+[
+.B -ad
+] [
+.I old
+[
+.I new
+] ]
+.SH DESCRIPTION
+.I Dirdiff
+computes the difference of two directories and outputs
+two
+.IR rc (1)
+lists,
+.L added,
+and
+.L deleted
+which describe the differences.  With the
+.B -d
+flag, the deleted files are output;
+with
+.BR -a ,
+the added files are output.  These flags may be combined.
+The default new directory is
+.L .
+while the default old directory is yesterday's version of
+the same directory.  Files that are different are not
+considered.
+.SH EXAMPLE
+.IP
+.EX
+; dirdiff
+added=( xmlheap.c xmlmalloc.c )
+deleted=( heap.c xmlfree.c )
+; dirdiff -d
+heap.c xmlfree.c
+.EE
+.SH SOURCE
+.B /rc/bin/dirdiff
+.SH SEE ALSO
+.IR rc (1),
+.IR yesterday (1)
+.SH BUGS
+Beware of directories with frogs.