#!/bin/bash
## unchg -- undo an erroneous chg[sed] command -- by Eugene Reimer 2001;
##
## Copyright © 2001,2007 Eugene Reimer;  can be used, modified, copied, and distributed or sold under the terms of either the LGPL or the GPL (your choice);
## see http://www.gnu.org/licenses for the details of these terms.

while [ $# -gt 0 ] && [[ $1 == -* ]]; do        ##parse the options
  case "$1" in
  --tmp*)	TMPBKUP=1		;;
  --tes*|-t)	TEST=1			;;
  --h*|-\?)	CMD="help"; HELP=0	;;
  --v*|-v)	VERS=1			;;
  --)		shift; break		;;
  esac
  shift;                                        ##remove that arg
done
[ $VERS ] && echo "unchg version:$(date -r$0 +%y%m%d). Copyright 1998,2005 Eugene Reimer. Licensed under the GPL" && exit 0
[ "$CMD" = "" ] && [ $# -eq 0 ] && HELP=2
if [ $HELP ]; then
  echo "usage:  unchg options              file..."
  echo "   or:  unchg options --tmpbackup  file..."
  echo "Restores file F from F~ or from under /tmp where the filename under /tmp is as made by chg."
  echo "  --tmpbackup           backup found under /tmp, instead of tilde-file in current directory"
  echo "  --test | -t           just show which files would be affected, but change nothing"
  echo "  --help | -?           just show this info on usage"
  echo "  --version | -v        just show version info"
  exit $HELP;                                   ##exit
fi
for f in "$@"; do
  [ -f "$f" ] || continue
  fbk="$f~";  [ $TMPBKUP ] && fbk=/tmp/bk-chg-$(fullnameNOSLASH "$f")	##(A) tilde-bkup in same dir;  (B) bkup under /tmp dir
  [ -f "$fbk" ] || { echo "##---$fbk not found---";  continue; }	##backup doesnot exist: inform user, and continue
  if [ $TEST ]; then
    echo "/bin/mv -fv -- \"$fbk\" \"$f\""				##just SHOW the mv command
  else
   #/bin/mv -f  -- "$f" "$f~unchg$$"					##rename to temp for swap-renaming  YANKED
    /bin/mv -fv -- "$fbk" "$f"						##EXECUTE the mv command, with informative msg
   #/bin/mv -f  -- "$f~unchg$$" "$fbk"					##rename temp for swap-renaming so next unchg is a redo  YANKED
  fi
done


exit
CONSIDER: making --tmp the default (only) backup option in chg??
IDENTIFYING backup-copies "made" on a certain date:  display the "status-chg" timestamp, using:  d-status  (or ls -c --full);

2005may23:  added --tmpbackups option, to restore from /tmp/bk-chg-$(fullnameNOSLASH $f)
2007jan30:  use /bin/mv to ensure my sdb6-backups are unaffected  (as they are by chg)
2010-05-02:  while working on weblinkcheck.cron in a test-run, unchg, try-again mode, realized I'd be happier without SWAP-style renaming;
	ie: when in doubt about whether or not I've done the undoing, would rather have a 2nd undo-attempt fail (than be a redo);  ==YANKED the swap-renaming;