Admin/isasync

fixed comment

#!/usr/bin/env bash
#
# $Id$
#
# mirror script for Isabelle distribution or website


## diagnostics

PRG=`basename "$0"`

usage()
{
  echo
  echo "Usage: $PRG [OPTIONS] DEST"
  echo
  echo "  Options are:"
  echo "    -h    print help message"
  echo "    -n    dry run, don't do anything, just report what would happen"
  echo "    -w    mirror whole Isabelle website"
  echo "    -d    delete files that are not on the server (BEWARE!)"
  echo
  exit 1
}

fail()
{
  echo "$1" >&2
  exit 2
}


## process command line

# options

HELP=""
ARGS=""
SRC="isabelle-distribution"

while getopts "hnwd" OPT
do
  case "$OPT" in
    h)
      HELP=true
      ;;
    n)
      ARGS="$ARGS -n"
      ;;
    w)
      SRC="isabelle-website"
      ;;
    d)
      ARGS="$ARGS --delete"
      ;;
    \?)
      usage
      ;;
  esac
done

shift `expr $OPTIND - 1`


# help

if [ -n "$HELP" ]; then
  cat <<EOF

Mirroring the Isabelle distribution or website
==============================================

The Munich site maintains an rsync server for the Isabelle
distribution or website.

The rsync tool is very smart and efficient in mirroring large
directory hierarchies.  See http://rsync.samba.org/ for more
information.  The $PRG script provides a simple front-end
for easy access to the Isabelle distribution.

The script can be either run in conservative or clean-sweep mode.

1) Basic mirroring works like this:

  $PRG /foo/bar

where /foo/bar refers to your local copy of the Isabelle distribution
(the base directory has to exist already).  This operation is
conservative in the sense that files are never deleted, thus garbage
may accumulate over time as our master copy is changed.

Avoiding garbage in your local copy requires some care.  Rsync
provides a way to delete all additional local files that are absent in
the master copy.  This provides an efficient way to purge large
directory hierarchies, even unwillingly in case that a wrong
destination is given!

2a) This will invoke a safe dry-run of clean-sweep mirroring:

  $PRG -dn /foo/bar

where additions and deletions will be printed without any actual
changes performed so far.

2b) Exact mirroring with actual deletion of garbage may be performed
like this:

  $PRG -d /foo/bar


After gaining some confidence in the workings of $PRG one
would usually set up some automatic mirror scheme, e.g. a daily cron
job run by the 'nobody' user.

Add -w to the option list in order to mirror the whole Isabelle website

EOF
  exit 0
fi


# arguments

[ $# -ne 1 ] && { echo "Bad arguments: $*"; usage; }

DEST="$1"; shift;


## main

exec rsync -va $ARGS "rsync://isabelle.in.tum.de/$SRC" "$DEST/"