feat: add support of xonsh shell to shellenv on Linux

[eugenesvk]

• Have you followed the guidelines in our Contributing document?
• Have you checked to ensure there aren't other open Pull Requests for the same change?
• Have you added an explanation of what your changes do and why you'd like us to include them?
• Have you written new tests for your changes? Here's an example.
  No, don't see any tests for shellenv, so don't know how write such a test. But I did test it in a xonsh shell
• Have you successfully run brew style with your changes locally?
• Have you successfully run brew typecheck with your changes locally?
• Have you successfully run brew tests with your changes locally?
  No, but I also have a few dozen failed tests within WSL on a fresh master. Also, haven't found any failures related to shellenv

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Currently on Linux the shellenv command only check the process list for the fish/t/csh shells and otherwise prints out generic bash instructions
I've updated shellenv to also check for the xonsh shell and print out correct xonsh instructions that can be evaluated to update a xonsh environment and make Linuxbrew usable in xonsh
I've also updated the installation instructions with the relevant xonsh commands

[MikeMcQuaid]

Sorry, passing on this, xonsh is far too niche for us to justify merging this.

[anki-code]

Hi @MikeMcQuaid ! Thank you for the response.

I'm just wondering how did you determine the xonsh is "niche"? There are a few thought why it's not :)

• If we compare fish and xonsh repositories they have 16 vs 4.5 stars but fish was made 15 years ago and xonsh 5 years ago. The speed of growing xonsh is comparing to fish.
• Xonsh is in Top 10 Trending Python Projects On GitHub: 2020

Also I see just twenty simple lines in this PR that completely have no affect on other code.

[jonchang]

https://formulae.brew.sh/analytics/install-on-request/30d/

xonsh has 2 orders of magnitude less usage than these other shells.

[anki-code]

Thanks for the awesome link @jonchang! Couple of thoughts:

We can see that tcsh has extremely less counter than xonsh but it was supported. Discrepancy )
UPD: the logic understood

Most of xonsh installs are came from PyPi/Conda packages along with Python way (that is in top 10 in Brew). The comparing of the count of installations of binary shells with xonsh is mostly has the bias in the data.

For example the Xonsh shell has around 20,000 installs in conda just for a 1.5 month:

This not looks like xonsh is "niche". The fish shell has comparing number of installs (13,000) in brew for a month (and after 15 years of history).

And because I see just twenty simple lines in this PR that completely have no affect on other code I'm suggesting to pass it to the world, The Open Sourced World )

[jonchang]

tcsh is supported because it used to be the default shell for new users in macOS, is still distributed in the default install, and (for users who have migrated their user profile across all those versions) is still set as the user's shell. None of those are true for xonsh.

[anki-code]

@jonchang ah, got it about tcsh, thanks!

[anki-code]

I have a short check the PyPi stats and try to make overview by data.

• We see around 600 installs of xonsh directly from Brew.

• We see Python in top 5 by installs in Brew and in sum (3.8+3.9) Python has the 1st place.

  • This means that some users install Python using Brew and then install xonsh from PyPi. We can't directly compare installations of binary shells with Brew vs xonsh installations with Brew.

• We see around 6,000 of xonsh installs per month in PyPi (it's a half of the fish shell installs per month in Brew).

• We see around 20,000 installs of xonsh in Conda (it's around the counters of the fish shell in Brew).

• Finally if we compare stars of fish and xonsh repos: they have 16 vs 4.5 that means that xonsh just 3.5 times less than fish (remember that fish 15 y.o. vs 5 y.o. xonsh) and xonsh in top 10 trending.

As result the statement about xonsh is "niche" has no strong support.

@MikeMcQuaid please take a look on this simple PR again.

[MikeMcQuaid]

As result the statement about xonsh is "niche" has no strong support.

We'll agree to disagree.

@MikeMcQuaid please take a look on this simple PR again.

I did, I haven't changed my mind.

[anki-code]

For the xonsh users:

xontrib-linuxbrew - Add Homebrew's shell environment to xonsh shell.

[MikeMcQuaid]

xontrib-linuxbrew - Add Homebrew's shell environment to xonsh shell.

Great idea. If this gets more traction we can consider including it in Homebrew proper. Thanks @anki-code!