I’m sorry it took me some time to understand what the regression was.

Here’s a PR: Fetch all refs unless using Git :depth option by rhcarvalho · Pull Request #13713 · elixir-lang/elixir · GitHub, I think we can move the conversation there.

Thanks, @josevalim

Fetch a :ref was not working at all and, once I addressed the :ref bug, I could not make it work together with :ref. If you can figure it out, a PR is welcome.

Short ref (error) and full ref (ok):

root@214431fdf2a5:/app# iex
Erlang/OTP 27 [erts-15.0] [source] [64-bit] [smp:8:8] [ds:8:8:10] [async-threads:1] [jit:ns]

Interactive Elixir (1.17.1) - press Ctrl+C to exit (type h() ENTER for help)
iex(1)> Mix.install [{:flame, github: "phoenixframework/flame", ref: "4600277"}]
* Getting flame (https://github.com/phoenixframework/flame.git - 4600277)
fatal: couldn't find remote ref 4600277
** (Mix.Error) Command "git --git-dir=.git fetch --force --quiet --progress origin 4600277" failed
    (mix 1.17.1) lib/mix.ex:588: Mix.raise/2
    (mix 1.17.1) lib/mix/scm/git.ex:136: Mix.SCM.Git.checkout/2
    (elixir 1.17.1) lib/file.ex:1665: File.cd!/2
    (mix 1.17.1) lib/mix/dep/fetcher.ex:64: Mix.Dep.Fetcher.do_fetch/3
    (mix 1.17.1) lib/mix/dep/converger.ex:238: Mix.Dep.Converger.all/9
    (mix 1.17.1) lib/mix/dep/converger.ex:170: Mix.Dep.Converger.init_all/8
    (mix 1.17.1) lib/mix/dep/converger.ex:110: Mix.Dep.Converger.all/4
    iex:1: (file)
iex(1)> Mix.install [{:flame, github: "phoenixframework/flame", ref: "46002774775fa5be947a970d7ff5aeefc0dd6707"}]
* Getting flame (https://github.com/phoenixframework/flame.git - 46002774775fa5be947a970d7ff5aeefc0dd6707)
remote: Enumerating objects: 767, done.        
remote: Counting objects: 100% (257/257), done.        
remote: Compressing objects: 100% (90/90), done.        
remote: Total 767 (delta 206), reused 181 (delta 164), pack-reused 510        
...
==> flame
Compiling 13 files (.ex)
Generated flame app
:ok

With full ref and depth:

root@214431fdf2a5:/app# iex
Erlang/OTP 27 [erts-15.0] [source] [64-bit] [smp:8:8] [ds:8:8:10] [async-threads:1] [jit:ns]

Interactive Elixir (1.17.1) - press Ctrl+C to exit (type h() ENTER for help)
iex(1)> Mix.install [{:flame, github: "phoenixframework/flame", ref: "46002774775fa5be947a970d7ff5aeefc0dd6707", depth: 1}]
* Getting flame (https://github.com/phoenixframework/flame.git - 46002774775fa5be947a970d7ff5aeefc0dd6707)
remote: Enumerating objects: 38, done.        
remote: Counting objects: 100% (38/38), done.        
remote: Compressing objects: 100% (32/32), done.        
remote: Total 38 (delta 0), reused 17 (delta 0), pack-reused 0        
Resolving Hex dependencies...
Resolution completed in 0.053s
...
==> flame
Compiling 13 files (.ex)
Generated flame app
:ok