Why builds from master are not tagged as such in brew?

[andreyorst]

Hi! I have a small question.
Currently, to build Emacs from the master branch, the readme suggests using:

brew install emacs-plus@31 [options] # install Emacs 31 (master)

Why not something like emacs-plus@master? I'm not familiar enough with brew yet, so I don't know. Maybe it's not possible to have this kind of name, or there are other reasons for that.

The reason why I'm asking is that I don't follow Emacs releases that closely, and I'm running Emacs built from master for several years already. Previously, I've built it myself on Linux, but since I got a Mac, I migrated to emacs-plus.

What bothers me with this naming convention is that it can break my configuration unexpectedly - I often use new features from the master branch in my configuration. However, when Emacs developers cut a new stable release, not all features from the master branch go there.

For emacs-plus, this means that one day, updating the installation, I might get a stable release instead of a build from master, so I'll end up with an installation that may not have all of the features that were there when it was a master build. Thus, my configuration would break.

One of the somewhat recent examples of that was when Emacs introduced package-vc-*, but not the :vc keyword for use-package, which was in master at the time of the release, so not including it was a bit strange.

So, why not something like emacs-plus@master, emacs-plus@head, or even emacs-plus@9999?

Sorry if this question was already asked - I searched over the issue tracker and discussions but couldn't find it.

[d12frosted]

Hey @andreyorst. Not sure I have something super intelligent to say, but let me try 😅

How versioning works

emacs-plus tracks Emacs versions because build requirements change between major releases - configure flags, dependencies, patches differ. This follows Homebrew conventions (gcc@13, postgresql@16).

• emacs-plus - alias to current stable (currently @30)
• emacs-plus@30 - Emacs 30 stable
• emacs-plus@31 - Emacs 31 (currently master)

Note: --HEAD builds from the version branch (e.g. emacs-30), not master. This matches how Emacs releases work.

When Emacs 31 releases, @31 will track stable and @32 will become the new master formula.

On stability

Version branches are cut from master at a point in time - you stop receiving new features, but nothing is taken away. The scenario you describe (config breaking because a feature disappears after a version cut) is (seems like) possible but rare - Emacs releases happen roughly once a year.

Meanwhile, master breaks things regularly. Over 10 years of maintaining emacs-plus, I've seen far more breakage from tracking master than from version transitions. So ironically, the versioned approach might give you more stability, not less.

That said, I understand wanting to not think about version numbers at all.

Would emacs-plus@master help?

We could add this as an alias that always points to the current development formula. That way we could have emacs-plus to point current stable release and emacs-plus@master to point to current unstable.

[andreyorst]

Thanks!

We could add this as an alias that always points to the current development formula. That way, we could have emacs-plus to point to the current stable release and emacs-plus@master to point to the current unstable.

I think that would make more sense than @31 building from master, until it doesn't. I have a script that rebuilds Emacs, that on Linux simply calls in configure with a set of options, and then make, and on macOS it simply calls brew with flags I need. Having emacs-plus@master would make things easier for me, as I wouldn't need to update the script, and/or face the fears I've described above.

Version branches are cut from master at a point in time - you stop receiving new features, but nothing is taken away.

IIRC, Emacs developers create a branch for the stable release, but the master branch continues living on its own, and things are selectively merged from master to the release branch when needed. There's always some time from branching to the release, and I update quite frequently, so maybe that explains why I got hit by that some times.

Meanwhile, master breaks things regularly. Over 10 years of maintaining emacs-plus, I've seen far more breakage from tracking master than from version transitions.

Huh, I maybe used Emacs from master for six years, but I can remember something breaking in a way that I had to wait for a fix or rollback to the previous commit like maybe three times. I was under the impression that the master branch is quite stable, since all crazy development happens in feature branches, and they are being tested quite extensively before merging into master.

Sadly (well, not exactly) I can't leave the master branch, as every time I want to, there's something cool that is not yet in a stable release, and once the stable release happens, I already use something else they've added :D

[d12frosted]

This has been implemented!

You can now use:

# Formula (compile from source)
brew install emacs-plus@master    # Always points to current development version

# Cask (pre-built binary)
brew install --cask emacs-plus-app@master

The @master alias currently points to emacs-plus@31. When Emacs 32 development starts, we'll update the alias to point to @32 before switching emacs-plus@31 to stable release, so your install command stays the same.

We also renamed the casks to follow homebrew-core conventions (not sure if you care):

• emacs-plus-app → stable (currently Emacs 30)
• emacs-plus-app@master → development (nightly builds)

See the https://github.com/d12frosted/homebrew-emacs-plus/blob/master/NEWS.org#2026-01-05 for full details.

Let me know if this works for your use case or if you have any thoughts on the naming!

[andreyorst]

Thanks! This works for me!

The @master alias currently points to emacs-plus@31. When Emacs 32 development starts, we'll update the alias to point to @32 before switching emacs-plus@31 to stable release, so your install command stays the same.

Small note: this seems to be a bit more manual on your side than I've expected. Is there a reason you need to do this as an alias? I was under impression that it should be possible to create @master and almost never touch it, only creating new versions for releases (again, I don't know much about brew)

[d12frosted]

It's not because of the way brew works. It's because of the way we, emacs-plus, expose versions. To avoid duplication, it's easier to just use alias. Whenever a new Emacs version is released, we just create a new file and that's it. Having this separation does result in some duplication, but on the other hand I can keep my head clean from thinking too much about compatibility between versions.

[andreyorst]

Understood, thanks!