TortoiseSVN pre-commit hook in C# - save yourself some troubles!

by Miłosz Orzeł 13. January 2013 19:24

Probably everyone who creates or debugs a program happens to make temporary changes to the code that make current task easier but should never get into the repository. And probably everyone has accidentally put such code into next revision. If you are lucky enough, mistake will be revealed quickly and the only result will be a bit of shame, if not...

If only there was a way to mark “uncommitable” code...

You can do it and it’s pretty simple!

TortoiseSVN lets you set so-called pre-commit hook. It’s a program (or script) that is run when user clicks “OK” button in “SVN Commit” window. Hook can for example check content of modified files and block commit when deemed appropriate. Tortoise hooks differ from Subversion hooks in that they are executed locally and not on the server that hosts the repository. You therefore don’t have to worry whether your hook will be accepted by the admin or if it works on the server (e.g. server may not have .NET installed), you also don’t affect the experience of other users of the repository. Client-side hooks are quicker too.

Detailed description of hooks can be found in „4.30.8. Client Side Hook Scripts” chapter of Tortoises help file.

Tortoise supports 7 kinds of hooks: start-commit, pre-commit, post-commit, start-update, pre-update, post-update and pre-connect. We are concerned with pre-commit action. The essence of the hook is to check whether one of added or modified files contains temporary code marker. Our marker may be a “NOT_FOR_REPO” text put into a comment placed above temporary code.

This is whole hook’s code – simple console application, that may save your ass :)

using System;
using System.IO;
using System.Text.RegularExpressions;

namespace NotForRepoPreCommitHook
{
    class Program
    {
        const string NotForRepoMarker = "NOT_FOR_REPO";

        static void Main(string[] args)
        {              
            string[] affectedPaths = File.ReadAllLines(args[0]);

            Regex fileExtensionPattern = new Regex(@"^.*\.(cs|js|xml|config)$", RegexOptions.IgnoreCase);

            foreach (string path in affectedPaths)
            {
                if (fileExtensionPattern.IsMatch(path) && File.Exists(path))
                {
                    if (ContainsNotForRepoMarker(path))
                    {
                        string errorMessage = string.Format("{0} marker found in {1}", NotForRepoMarker, path);
                        Console.Error.WriteLine(errorMessage);    
                        Environment.Exit(1);  
                    }
                }
            }             
        }

        static bool ContainsNotForRepoMarker(string path)
        {
            StreamReader reader = File.OpenText(path);

            try
            {
                string line = reader.ReadLine();

                while (line != null)
                {
                    if (line.Contains(NotForRepoMarker))
                    {
                        return true;
                    }

                    line = reader.ReadLine();
                }
            }
            finally
            {
                reader.Close();
            }  

            return false;
        }
    }
}

TSVN calls pre-commit hook with four parameters. We are interested only in the first one. It contains a path to *.tmp file. In this file there is a list of files affected by current commit. Each line is one path. After loading the list, files are filtered by extension (useful if you don’t want to process files of all types). Checking if file exists is also important – the list from *.tmp file contains paths for deleted files too! Detection of the marker represented by NotForRepoMarker constant is realized by ContainsNotForRepoMarker method. Despite its simplicity it provides good performance. On mine (middle range) laptop, 100 MB file takes less than a second to process. If marker is found, program exits with error code (value different than 0). Before quitting, information about which file contains the marker is sent to standard error output (via Console.Error). This message will get displayed in Tortoise window.

The code is simple, isn’t it? In addition, hook installation is also trivial!

To attach hook, choose “Settings” item from Tortoise’s context menu. Then select “Hook scripts” element and click “Add…” button. Such window will appear:

TSVN hooks configuration window

Set „Hook Type” to „Pre-Commit Hook”. Fill “Working Copy Path” field with a path to the directory that contains local copy of the repo (different folders can have different hooks). In “Command Line To Execute” field, set path to the application that implements the hook. Check “Wait for the script to finish” and “Hide the script while running” options (the latter will prevent console window from showing). Press “OK” button and voila, hook is installed!

Now mark some code with “NOT_FOR_REPO” comment and try to execute commit. You should see something like that:

Operation blocked by pre-commit hook

Notice the „Retry without hooks” button – it allows commit to be completed by ignoring hooks.

We now have a hook that prevents from temporary code submission. One may also want to create a hook that enforces log message to be filled, blocks *.log files commits etc. Your private hooks – you decide! And if some of the hooks will be usefull for the whole team, you can always remake them as Subversion hooks.

Tested on TortoiseSVN 1.7.8/Subversion 1.7.6.

Update 24.03.2014: Added emphasis to checking "Wait for the script to finish" option - without it hook will not block commits!

Update 17.09.2013: (additional info): You may set hook on a parent folder which contains multiple repositories checkouts. If you are willing to sacrifice a bit of performance for added protection you may resign from filtering files before checking for NotForRepoMarker marker.  

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