Mercurial: The Definitive Guide

Which Files to Manage, and Which to Avoid

Revision control systems are generally best at managing text files that are written by humans, such as source code, where the files do not change much from one revision to the next. Some centralized revision control systems can also deal tolerably well with binary files, such as bitmap images.

For instance, a game development team will typically manage both its source code and all of its binary assets (e.g., geometry data, textures, map layouts) in a revision control system.

Because it is usually impossible to merge two conflicting modifications to a binary file, centralized systems often provide a file locking mechanism that allows a user to say “I am the only person who can edit this file.”

Compared to a centralized system, a distributed revision control system changes some of the factors that guide decisions over which files to manage and how.

For instance, a distributed revision control system cannot, by its nature, offer a file locking facility. There is thus no built-in mechanism to prevent two people from making conflicting changes to a binary file. If you have a team where several people may be editing binary files frequently, it may not be a good idea to use Mercurial—or any other distributed revision control system—to manage those files.

When storing modifications to a file, Mercurial usually saves only the differences between the previous and current versions of the file. For most text files, this is extremely efficient. However, some ...