Installing with --HEAD flag fails

[captainbarbosa]

I've been poking around and trying to install danger-swift with the --HEAD command. Per the help page, brew install --help says:

 --HEAD                       If formula defines it, install the HEAD
                              version, aka. master, trunk, unstable.

When trying this locally, brew install danger/tap/danger-swift --HEAD, the installation fail with the following:

Expand output

brew install danger/tap/danger-swift --HEAD                                                        9:24:56 
==> Installing danger-swift from danger/tap
==> Installing dependencies for danger/tap/danger-swift: danger/tap/danger-js
==> Installing danger/tap/danger-swift dependency: danger/tap/danger-js
==> Downloading https://github.com/danger/danger-js/releases/download/9.2.10/danger-macos.zip
Already downloaded: /Users/.../Library/Caches/Homebrew/downloads/9a228f1e3586bba7ed280a25387fd4bd5ec2578b21d912a86122feb89229b257--danger-macos.zip
Warning: This keg was marked linked already, continuing anyway
🍺  /usr/local/Cellar/danger-js/9.2.10: 3 files, 83.0MB, built in 4 seconds
==> Installing danger/tap/danger-swift --HEAD
==> Cloning https://github.com/danger/danger-swift.git
Updating /Users/nadiabarbosa/Library/Caches/Homebrew/danger-swift--git
==> Checking out branch master
Already on 'master'
Your branch is up to date with 'origin/master'.
HEAD is now at a67db06 Merge pull request #329 from lucasmpaim/fix/build-on-xcode-11.4
==> make install PREFIX=/usr/local/Cellar/danger-swift/HEAD-a67db06
Last 15 lines from /Users/.../Library/Logs/Homebrew/danger-swift/01.make:
[7/12] Compiling Runner Edit.swift
[8/12] Compiling OctoKit Configuration.swift
[9/13] Linking danger-swift
[10/13] Compiling Danger BitBucketCloud.swift
[11/15] Compiling Danger-Swift Fake.swift
[12/15] Linking libDanger.dylib
[13/15] Linking libDangerDeps.dylib
[14/15] Compiling DangerFixtures CustomGitHubDSL.swift
[15/15] Linking libDangerFixtures.dylib
mkdir -p /usr/local/Cellar/danger-swift/HEAD-a67db06/bin
mkdir -p /usr/local/Cellar/danger-swift/HEAD-a67db06/lib/danger
cp -f .build/release/danger-swift /usr/local/Cellar/danger-swift/HEAD-a67db06/bin/danger-swift
cp -f .build/release/libDanger.* .build/release/Danger.swiftdoc .build/release/Danger.swiftmodule .build/release/OctoKit.swiftdoc .build/release/OctoKit.swiftmodule .build/release/RequestKit.swiftdoc .build/release/RequestKit.swiftmodule .build/release/Logger.swiftdoc .build/release/Logger.swiftmodule .build/release/DangerShellExecutor.swiftdoc .build/release/DangerShellExecutor.swiftmodule /usr/local/Cellar/danger-swift/HEAD-a67db06/lib/danger
cp: .build/release/libDanger.dylib.dSYM is a directory (not copied).
make: *** [install] Error 1

If reporting this issue please do so at (not Homebrew/brew or Homebrew/core):
  https://github.com/danger/homebrew-tap/issues

These open issues may also help:
Failing to install danger-swift via HomeBrew https://github.com/danger/homebrew-tap/issues/2

I double checked the Homebrew documentation and I found this section, and it appears that as long as the Formulae file has the head parameter set, this should work. Iin danger-swift.rb, it looks like its there,

https://github.com/danger/homebrew-tap/blob/master/danger-swift.rb#L7:

head "https://github.com/danger/danger-swift.git"

...but I'm not sure why the installation isn't succeeding 🤔

Thanks for your help! For now, I'm just building from source so its not a blocker for me.