What's new in Mercurial 4.0

What's new in Mercurial 4.0

Mercurial (HG) 4.0 was released yesterday (1st of November 2016). Mercurial follows a time-based release plan, which means that a new Major version is out four times in a year. Mercurial is a good alternative for Git and Subversion if you like the benefits of having the whole repository on your local machine but don't like the complexity of Git. Even though the release is numbered as 4.0, which would be considered a backward incompatible version, the official release notes claim it should be a usual pain-free upgrade.

Notable changes

Many changes new in Mercurial 4.0 are heavily targeted towards power users or developers who utilize Mercurial in their own apps. As an example, Mercurial 4.0 adds the support for customizable output to hg version, hg grep and hg config commands. The Customizable output gives users fine-grained control for numerous tasks without adding lots of new command line switches to Mercurial itself. The customizable format uses templates that can be defined by the user.

Templating has received more other improvements as well. There are now new template keywords and functions, such as termwidth, mod(a, b), relpath(path) and the ability to conduct basic arithmetic operations, such as termwidth -10.

Internal enhancements

One of the internal enhancements, which go really to the core, is the improvement of the Python 3 support. The support for Python 3 is at very early stage. At the time of writing, only some parts of the testing process were fully functional under Python 2.6, 2.7 and 3.5 respectively. For additional information regarding Python 3 status, there's a page in Mercurial official Wiki.


Notable changes in Mercurial 4.0 release are directed more towards power users or the development team themselves. It's good to see Mercurial being live and pushing new releases, but it would be even better to see some nice end-user features being pushed out. Now there's little to no benefit in updating the local hg installation. You can read the official release notes and overview of changes from the official Site and comment below, whether you agree or not.

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