Comment by timv

I think that the hate that gets lumped on mercurial's branches, though understandable, is a bit unfair

Disclaimer, it's been years since I used hg as my primary DVCS. So some of my thoughts here might be out of date, or have a misrecollection.

> branching in hg is pretty much broken*

It really isn't. It's absolutely not suited for the task that many people want to use it for, but it's totally fitting with the intended use case and the "history is immutable" philosophy of mercurial.

Using mercurial branches for anything resembling feature branching is a bad idea. But mercurial branches are perfect for things like ongoing lines of development. So, for a project like PostgreSQL, you'd have a "master" (default) branch for the head of development and then once a release goes into maintenance mode you create a new branch for "postgres-9.4" and any fixes that need to be applied to that release will be made to the maintenance branch.

Following hg's "immutable history" policy the fact that the commit was performed on a maintenance branch is tracked forever. And it should be because the purpose of your source control is to track those kinds of things: "This is the branch we used for maintenance releases of version X.Y.Z, it is now closed since we no longer support that version"

The issues with mercurial's branches are:

- For a long time they were the only concept in hg that had a simple name and looked like "multiple lines of development". Even though hg supported multiple heads and multiple lightweight clones, neither of those had commands or features with a clear and simple name, so they people turned to "branches" expecting them to do what they wanted even when they were a bad fit.

- "branch" is very general name that is often used (quite rightly) to refer to a bunch of slightly different ways of working with multiple concurrent versions. In general use it might refer simply having 2 developers who both produce independent changes from the same parent. Or to intentionally having multiple short lived lines of development based around feature. Or splitting of development right before a release so that the "release branch" is stable. Etc. Yet the feature in hg that is called "branch" is useful for only some of those things. It would have been better to call it a "development line" or something like that.

- It took far too long for hg to get a builtin way to refer to named heads (bookmarks). The model assumed that each repository (clone) would only ever want to have 1 head on each branch (development line) and that producing multiple heads was a problem that ought to be resolved as soon as possible. There's a lot of history behind that approach (almost every CVS and SVN team I ever worked with did that), but DVCS tools made it easier to move away from that, yet official hg support lagged.

So even today, the "branch" concept in hg is only useful for a small number of cases, and the "bookmarks" concept is what most people want, but they're separate things with names that don't align with expectations.