source: hooks/pre-revprop-change.tmpl

#!/bin/sh

# PRE-REVPROP-CHANGE HOOK
#
# The pre-revprop-change hook is invoked before a revision property
# is added, modified or deleted.  Subversion runs this hook by invoking
# a program (script, executable, binary, etc.) named 'pre-revprop-change'
# (for which this file is a template), with the following ordered
# arguments:
#
#   [1] REPOS-PATH   (the path to this repository)
#   [2] REV          (the revision being tweaked)
#   [3] USER         (the username of the person tweaking the property)
#   [4] PROPNAME     (the property being set on the revision)
#   [5] ACTION       (the property is being 'A'dded, 'M'odified, or 'D'eleted)
#
#   [STDIN] PROPVAL  ** the new property value is passed via STDIN.
#
# If the hook program exits with success, the propchange happens; but
# if it exits with failure (non-zero), the propchange doesn't happen.
# The hook program can use the 'svnlook' utility to examine the 
# existing value of the revision property.
#
# WARNING: unlike other hooks, this hook MUST exist for revision
# properties to be changed.  If the hook does not exist, Subversion 
# will behave as if the hook were present, but failed.  The reason
# for this is that revision properties are UNVERSIONED, meaning that
# a successful propchange is destructive;  the old value is gone
# forever.  We recommend the hook back up the old value somewhere.
#
# The default working directory for the invocation is undefined, so
# the program should set one explicitly if it cares.
#
# On a Unix system, the normal procedure is to have 'pre-revprop-change'
# invoke other programs to do the real work, though it may do the
# work itself too.
#
# Note that 'pre-revprop-change' must be executable by the user(s) who will
# invoke it (typically the user httpd runs as), and that user must
# have filesystem-level permission to access the repository.
#
# On a Windows system, you should name the hook program
# 'pre-revprop-change.bat' or 'pre-revprop-change.exe',
# but the basic idea is the same.
#
# The hook program runs in an empty environment, unless the server is
# explicitly configured otherwise.  For example, a common problem is for
# the PATH environment variable to not be set to its usual value, so
# that subprograms fail to launch unless invoked via absolute path.
# If you're having unexpected problems with a hook program, the
# culprit may be unusual (or missing) environment variables.
#
# CAUTION:
# For security reasons, you MUST always properly quote arguments when
# you use them, as those arguments could contain whitespace or other
# problematic characters. Additionally, you should delimit the list
# of options with "--" before passing the arguments, so malicious
# clients cannot bootleg unexpected options to the commands your
# script aims to execute.
# For similar reasons, you should also add a trailing @ to URLs which
# are passed to SVN commands accepting URLs with peg revisions.
#
# Here is an example hook script, for a Unix /bin/sh interpreter.
# For more examples and pre-written hooks, see those in
# the Subversion repository at
# http://svn.apache.org/repos/asf/subversion/trunk/tools/hook-scripts/ and
# http://svn.apache.org/repos/asf/subversion/trunk/contrib/hook-scripts/


REPOS="$1"
REV="$2"
USER="$3"
PROPNAME="$4"
ACTION="$5"

if [ "$ACTION" = "M" -a "$PROPNAME" = "svn:log" ]; then exit 0; fi

echo "Changing revision properties other than svn:log is prohibited" >&2
exit 1