What is mercurial?

Mercurial is a free, open‑source tool that helps developers keep track of changes in their code. Think of it like a super‑smart notebook that records every edit you make to files, lets you go back to earlier versions, and lets multiple people work on the same project without stepping on each other’s toes.

Let's break it down

  • Repository: a folder where Mercurial stores all your files and their history.
  • Commit: a snapshot of the project at a specific moment; each commit has a unique ID.
  • Branch: a separate line of development, useful for trying new features without affecting the main code.
  • Merge: combining changes from different branches back together.
  • Push / Pull: sending your commits to a remote server (push) or getting others’ commits from that server (pull).

Why does it matter?

Without a version‑control system, you’d have to manually copy files, rename them, and hope you don’t lose work. Mercurial gives you:

  • Safety: you can always revert to a previous state.
  • Collaboration: many people can edit the same project simultaneously.
  • History: you can see who changed what and why, which helps debugging and accountability.

Where is it used?

Mercurial is used by software teams of all sizes, especially in projects that value speed and simplicity. Notable examples include the Python programming language’s source code (for a time), large open‑source projects like OpenStack, and many internal company codebases that prefer Mercurial over other tools.

Good things about it

  • Speed: operations are fast, even on large projects.
  • Ease of use: commands are straightforward and consistent.
  • Cross‑platform: works on Windows, macOS, Linux, and even mobile devices.
  • Extensible: a rich set of plugins and extensions let you add features like code review or CI integration.
  • Strong data integrity: every change is checksummed, so corruption is detected early.

Not-so-good things

  • Smaller community: compared to Git, fewer tutorials, tools, and third‑party integrations exist.
  • Less industry adoption: many companies have standardized on Git, making Mercurial skills less marketable.
  • Limited GUI options: fewer graphical clients are available, which can be a hurdle for non‑technical users.
  • Branch handling: while functional, Mercurial’s branching model is sometimes considered less flexible than Git’s.