Wednesday, July 14, 2010

Managing a Google Code project with Mercurial

As a recent convert to Mercurial, I started my last Google Code Project using Mercurial instead of Subversion. In this post I won't go into details as regards SVN vs. Mercurial, but to SVN users I suggest you check out Mercurial; starting with Joel Spolsky's tutorial and then moving on to the Mercurial: The Definitive Guide online book.


First you need to have Mercurial installed. To download, visit the Mercurial Downloads page and follow the instructions for your respective Operating System.

After installing Mercurial, fire up your terminal and type: hg version
This should display something similar to the following:

Mercurial Distributed SCM (version 1.4.3)

Copyright (C) 2005-2010 Matt Mackall  and others
This is free software; see the source for copying conditions. There is NO

If you see that on your terminal, then Mercurial has been installed successfully and you're ready to continue.

Setting up a default user

Thanks to Scott Willeke who reminded me about this in the comments

Once Mercurial is successfully installed, you need to setup a default user that will be responsible for commiting changes to the repository. If you're on Windows, create a Mercurial.ini file or a .hgrc file in your %USERPROFILE% folder and if you're on a Linux create an .hgrc file in your $HOME directory.

On my windows box, I created a Mercurial.ini file in C:\Users\Andreas\Mercurial.ini.

Once you create this config file, add the following in it:

username = Your Name <your_email_address>

You can add many other options to this config file (more details can be found here) but for the moment, this is sufficient.

Initiating the Project

To create the project on the hosting page, visit Google Code's Create Project page. When choosing a Version Control system, make sure that you choose Mercurial:

For the purposes of this demonstration, let's assume that our project name is myhgproject.

After setting all the required project details, you will be taken to your project's home page; your url takes this form:

Now we need to set up our local repository on the machine and push everything to the online repository. To do this, first visit the Source page of your project ( and copy the clone command: hg clone myhgproject

This command will make a clone of the online repository on your machine:

So at the moment, we have our project directory (not revisioned) ~/myproject and a new directory ~/myhgproject that Mercurial created for us.

Now we need to move our project files from the directory we used to work in to the new folder ~/myhgproject:

With this, we now have everything in our new folder and are now ready to add these new files to our local repository:

The hg add command adds the files to the repository on the next commit, so the next step is to commit these files to our local repository:

Note that up till now, we still haven't pushed our files to the online repository. We have only committed our files to our local repository online. Uploading these files is the next step.

To do this, you must first retrieve your password from this page: Now using your google username and that password, we can push our files to the online repository:

For the purposes of this demonstration, let's assume my password is: AbCdEfGHiJ12

The files have now been pushed to the online repository.

Working on the project

Now that everything has been pushed to the online repository, you are now ready to start working normally on your project.

Your average routine will be working on some files, committing to the local repository with hg com -m "your commit message" and then when you have a working copy, push to the online repository with hg push.

Pushing without entering the url

Note that to avoid typing in your login credentials and the url every time you want to push, you can add these details in the hgrc file located in the .hg directory of your project.

Open up .hg/hgrc and add the following lines (obviously change according to your project):

default =

If you don't have the hgrc file, you can manually add it yourself.

Note that now you must now make sure that your hgrc file is well protected since it contains your login details in plain text.