With a distributed version control system you basically do not have a central code repository but everyone has its own branch. To can clone a branch and you always get the full history of the whole branch on your system. You commit into your own branch and you can push your changes to other repositories and other people can pull from you.

The main advantages of distributed version control systems are

Another popular distributed version control systems is Git .

Mercurial is a distributed version control system. Mercurial is used by Oracle for the OpenJDK development and offered as a option by Google in Google hosting.

Mercurial is written in Python. Mercurial has a command-line interface. Eclipse provides also a plug-in to use Mercurial.

Install Mercurial on Ubuntu via:

sudo apt-get install mercurial 

The installation of Mercurial for other platforms is described in Mercurial installation .

You find binary packages for Mercurial on Window on Binary packages for Windows.

The following will demonstrate a short development cycle using the command line interface of Mercurial.

You will create a new Mercurial repository, create a new Java project and commit the changes to your Mercurial repository.

The command for using Mercurial on the command line is "hg".

Check that you are using Mercurial version 1.3 or higher:

hg --version 

Create and switch to your desired work directory .

Initialize a new Mercurial repository with:

hg clone https://yourproject.googlecode.com/hg/ name_of_directory_for_the_clone 

hg clone https://yourproject.googlecode.com/hg/ name_of_directory_for_the_clone 

Eclipse creates a lot of metadata with regards to the current status of the Eclipse workbench. Also Eclipse creates compiled version in the directory bin. This data should not be placed in the mercurial repository. Create the file ".hgignore" in the same directory as the hg project.

# switch to regexp syntax.
syntax: regexp
^\.metadata
^de.vogella.mercurial.firstproject/bin$ 

Start Eclipse and use the new directory as workspace. Create a new Java project "de.vogella.mercurial.firstproject". Create the following Java class.

package de.vogella.mercurial.firstproject;

public class Test {

  
/**
   * @param args
   */
  public static void main(String[] args) {
    System.out.println("Hello Mercurial");
  }

} 

Add the project to Mercurial.

hg commit -A -m 'Commit with automatic addremove' 

Commit.

hg commit -m "Create new project" 

If you have checked out the Mercurial project from another site you can push your changes to the repository.

hg push 

Check the history via:

hg log 

Rename your Java class to "TestNewName" and create a new class "Test2".

package de.vogella.mercurial.firstproject;

public class Test2 {

  
/**
   * @param args
   */
  public static void main(String[] args) {
    System.out.println("Hello Mercurial");
    System.out.println("This is a new class");
  }

} 

Add the new files to Mercurial.

hg commit -A -m 'Commit with automatic addremove' 

A rename in Java removes the old file. Mercurial will report these files as missing (hg status). You can use the following command to automatically add the new files and remove the deleted.

Add the new files to Mercurial.

hg addremove 

You can now commit. The -A flag in the commit command would also automatically add and remove new files.

hg add . 

To see the changes use the status command. diff we show the differences.

hg log
hg diff 

You can revert the changes via "hg revert".

hg revert de.vogella.mercurial.firstproject/src/de/vogella/mercurial/firstproject/Test.java 

http://mercurial.selenic.com/ Mercurial Homepage

http://mercurial.selenic.com/wiki/ Mercurial Wiki

http://hgbook.red-bean.com/ Free Online Mercurial Book from http://hgbook.red-bean.com/

http://bitbucket.org/ Mercurial Hosting service

http://hgbook.red-bean.com/read/ Mercurial: The Definitive Guide

http://code.google.com/p/support/wiki/ConvertingSvnToHg How to convert svn to Mercurial at Google hosting

http://www.javaforge.com/project/HGE EclipseMercurial plug-in homepage

http://javaforge.com/wiki/76402 EclipseMercurial change logs

http://www.javaforge.com/project/HGE/tracker Mercurial Eclipse Bugtracker

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