How to require commit messages in VisualSVN server?

I'm glad you asked this question. This is our pre-commit hook script written in common Windows Batch. It denies commit if the log message is less than 6 characters. Just put the pre-commit.bat to your hooks directory.

pre-commit.bat

setlocal enabledelayedexpansion

set REPOS=%1
set TXN=%2

set SVNLOOK="%VISUALSVN_SERVER%\bin\svnlook.exe"

SET M=

REM Concatenate all the lines in the commit message
FOR /F "usebackq delims==" %%g IN (`%SVNLOOK% log -t %TXN% %REPOS%`) DO SET M=!M!%%g

REM Make sure M is defined
SET M=0%M%

REM Here the 6 is the length we require
IF NOT "%M:~6,1%"=="" goto NORMAL_EXIT

:ERROR_TOO_SHORT
echo "Commit note must be at least 6 letters" >&2
goto ERROR_EXIT

:ERROR_EXIT
exit /b 1

REM All checks passed, so allow the commit.
:NORMAL_EXIT
exit 0

VisualSVN Server 3.9 provides the VisualSVNServerHooks.exe check-logmessage pre-commit hook that helps you reject commits with empty or short log messages. See the article KB140: Validating commit log messages in VisualSVN Server for instructions.

Besides the built-in VisualSVNServerHooks.exe, VisualSVN Server and SVN in general uses a number of hooks to accomplish tasks like this.

• start-commit — run before commit transaction begins, can be used to do special permission checking
• pre-commit — run at the end of the transaction, but before commit. Often used to validate things such as a non zero length log message.
• post-commit — runs after the transaction has been committed. Can be used for sending emails, or backing up repository.
• pre-revprop-change — runs before a revision property change. Can be used to check permissions.
• post-revprop-change — runs after a revision property change. Can be used to email or backup these changes.

You need to use the pre-commit hook. You can write it yourself in just about any language your platform supports, but there are a number of scripts on the web. Googling "svn precommit hook to require comment" I found a couple that looked like they would fit the bill:

• Perl Script
• Python Script

The technical answers to your question have already been given. I'd like to add the social answer, which is: "By establishing commit message standards with your team and getting them to agree (or accept) reasons why one would need expressive commit messages"

I've seen so many commit messages that said "patch", "typo", "fix" or similar that I've lost count.

Really - make it clear to everybody why you'd need them.

Examples for reasons are:

• Generated Changenotes (well - this'd actually make a nice automatic tool to enforce good messages if I know that they will be (with my name) publically visible - if only for the team)
• License issues: You might need to know the origin of code later, e.g. should you want to change the license to your code (Some organizations even have standards for commit message formatting - well, you could automate the checking for this, but you'd not necessarily get good commit messages with this)
• Interoperability with other tools, e.g. bugtrackers/issue management systems that interface with your version control and extract information from the commit messages.

Hope that helps, additionally to the technical answers about precommit hooks.

What VisualSVN offers you to enter as hooks are "Windows NT command scripts", which are basically batch files.

Writing if-then-else in batch files is very ugly and probably very hard to debug.

It will look something like the following (search for pre-commit.bat) (not tested):

SVNLOOK.exe log -t "%2" "%1" | grep.exe "[a-zA-Z0-9]" > nul || GOTO ERROR
GOTO OK
:ERROR
ECHO "Please enter comment and then retry commit!"
exit 1
:OK
exit 0 

You need a grep.exe on the path, %1 is the the path to this repository, %2 the name of the txn about to be committed. Also have a look at the pre-commit.tmpl in the hooks directory of your repository.

Use this pre-commit hook on Windows. It's written in Windows Batch and uses grep command-line utility to check the commit length.

svnlook log -t "%2" "%1" | c:\tools\grep -c "[a-zA-z0-9]" > nul
if %ERRORLEVEL% NEQ 1 exit 0

echo Please enter a check-in comment 1>&2
exit 1

Remember that you'll need a copy of grep, I recommend the gnu tools version.

Here's a Windows Shell JScript that you can use by specifying the hook as:

%SystemRoot%\System32\CScript.exe //nologo <..path..to..script> %1 %2

It's pretty easy-to-read, so go ahead an experiment.

BTW, the reason to do this in JScript is that it does not rely on any other tools (Perl, CygWin, etc.) to be installed.

if (WScript.Arguments.Length < 2)
{
    WScript.StdErr.WriteLine("Repository Hook Error: Missing parameters. Should be REPOS_PATH then TXN_NAME, e.g. %1 %2 in pre-commit hook");
    WScript.Quit(-1);
}

var oShell = new ActiveXObject("WScript.Shell");
var oFSO = new ActiveXObject("Scripting.FileSystemObject");

var preCommitStdOut = oShell.ExpandEnvironmentStrings("%TEMP%\\PRE-COMMIT." + WScript.Arguments(1) + ".stdout");
var preCommitStdErr = oShell.ExpandEnvironmentStrings("%TEMP%\\PRE-COMMIT." + WScript.Arguments(1) + ".stderr");

var commandLine = "%COMSPEC% /C \"C:\\Program Files\\VisualSVN Server\\bin\\SVNLook.exe\" log -t ";

commandLine += WScript.Arguments(1);
commandLine += " ";
commandLine += WScript.Arguments(0);
commandLine += "> " + preCommitStdOut + " 2> " + preCommitStdErr;


// Run Synchronously, don't show a window
// WScript.Echo("About to run: " + commandLine);
var exitCode = oShell.Run(commandLine, 0, true);

var fsOUT = oFSO.GetFile(preCommitStdOut).OpenAsTextStream(1);
var fsERR = oFSO.GetFile(preCommitStdErr).OpenAsTextStream(1);

var stdout = fsOUT && !fsOUT.AtEndOfStream ? fsOUT.ReadAll() : "";
var stderr = fsERR && !fsERR.AtEndOfStream ? fsERR.ReadAll() : "";

if (stderr.length > 0)
{
    WScript.StdErr.WriteLine("Error with SVNLook: " + stderr);
    WScript.Quit(-2);
}

// To catch naught commiters who write 'blah' as their commit message

if (stdout.length < 5)
{
    WScript.StdErr.WriteLine("Please provide a commit message that describes why you've made these changes.");
    WScript.Quit(-3);
}

WScript.Quit(0);

Prior to adding commit hooks to my server, I just distributed svnprops to the TortoiseSVN clients.

So, as an alternative:

In TortoiseSVN -> Properties property name - add/set tsvn:logminsize appropriately.

This of course is no guarantee on the server as clients/users can opt not to do it, but you can distribute svnprops files if you like. This way, users don't have to set their own values - you can provide them to all users.

This also works for things like bugtraq: settings to link issue tracking stuff in the logs.