默认是不允许修改的。

在版本库的hooks目录下加入一个批处理文件：pre-revprop-change.bat

@ECHO OFF

set repos=%1
set rev=%2
set user=%3
set propname=%4
set action=%5
::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::
:: Only allow changes to svn:log. The author, date and other revision
:: properties cannot be changed
::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::
if /I not '%propname%'=='svn:log' goto ERROR_PROPNAME
::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::
:: Only allow modifications to svn:log (no addition/overwrite or deletion)
::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::
if /I not '%action%'=='M' goto ERROR_ACTION
::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::
:: Make sure that the new svn:log message contains some text.
::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::::
set bIsEmpty=true
for /f "tokens=*" %%g in ('find /V ""') do (
set bIsEmpty=false
)

if '%bIsEmpty%'=='true' goto ERROR_EMPTY
goto :eof
:ERROR_EMPTY
echo Empty svn:log properties are not allowed. >&2
goto ERROR_EXIT
:ERROR_PROPNAME
echo Only changes to svn:log revision properties are allowed. >&2
goto ERROR_EXIT
:ERROR_ACTION
echo Only modifications to svn:log revision properties are allowed. >&2
goto ERROR_EXIT
:ERROR_EXIT
exit 1

然后用TortoiseSVN->显示日志->选择待修改日志->右键：编辑日志信息。