Mercurial: The Definitive Guide

Migrating from Subversion

Subversion is currently the most popular open source revision control system. Although there are many differences between Mercurial and Subversion, making the transition from Subversion to Mercurial is not particularly difficult. The two have similar command sets and generally uniform interfaces.

Philosophical Differences

The fundamental difference between Subversion and Mercurial is of course that Subversion is centralized, while Mercurial is distributed. Since Mercurial stores all of a project’s history on your local drive, it only needs to perform a network access when you want to explicitly communicate with another repository. In contrast, Subversion stores very little information locally, and the client must thus contact its server for many common operations.

Subversion more or less gets away with not having a well-defined notion of a branch: which portion of a server’s namespace qualifies as a branch is a matter of convention, with the software providing no enforcement. Mercurial treats a repository as the unit of branch management.

Scope of commands

Since Subversion doesn’t know what parts of its namespace are really branches, it treats most commands as requests to operate at and below whatever directory you are currently visiting. For instance, if you run svn log, you’ll get the history of whatever part of the tree you’re looking at, not the tree as a whole.

Mercurial’s commands behave differently, by defaulting to operating over an entire repository. ...