Brew audit --git fails if taps default branch is not master

[PurpleBooth]

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• ran brew update and can still reproduce the problem?
• ran brew doctor, fixed all issues and can still reproduce the problem?
• ran brew config and brew doctor and included their output with your issue?

What you were trying to do (and why)

I have a personal tap at PurpleBooth/homebrew-repo. I recently became uncomfortable using the word "master", so I changed the default branch to "main". It worked fine until a recent change to how audit works (which is itself called by brew test-bot, which is what's blocking me from building bottles in a sensible way)

I believe this is related to this line, #7684 and Homebrew/homebrew-test-bot#422

What happened (include command output)

Command output

$ brew audit --git purplebooth/repo/readable-name-generator --online

Error: undefined method +' for nil:NilClass Please report this issue: https://docs.brew.sh/Troubleshooting /usr/local/Homebrew/Library/Homebrew/dev-cmd/audit.rb:789:in audit_revision_and_version_scheme'

/usr/local/Homebrew/Library/Homebrew/dev-cmd/audit.rb:931:in block in audit' /usr/local/Homebrew/Library/Homebrew/dev-cmd/audit.rb:924:in each'

/usr/local/Homebrew/Library/Homebrew/dev-cmd/audit.rb:924:in audit' /usr/local/Homebrew/Library/Homebrew/dev-cmd/audit.rb:128:in block in audit'

/usr/local/Homebrew/Library/Homebrew/dev-cmd/audit.rb:114:in each' /usr/local/Homebrew/Library/Homebrew/dev-cmd/audit.rb:114:in audit'

/usr/local/Homebrew/Library/Homebrew/brew.rb:110:in `
'

What you expected to happen

The audit to pass, or flag a problem with my configuration. I believe it would pass.

Ideally, the branch would be detected, rather than assuming master.

Step-by-step reproduction instructions (by running brew commands)

The exact thing I did was this. I might resolve this example because I like having binaries built

brew update
brew tap PurpleBooth/repo
brew audit --git purplebooth/repo/readable-name-generator --online

I've left a broken tap at

brew tap PurpleBooth/broken
brew audit --git purplebooth/broken/game-of-life

To create the git repository

git init .
git checkout -b main
git branch -d master
mkdir Formula
## The formula isn't important, it's just something to audit
cat > Formula/game-of-life.rb <<EOF
class GameOfLife < Formula
  desc "PurpleBooth's implementation of Conway's Game of life"
  homepage "https://github.com/PurpleBooth/game-of-life"
  url "https://github.com/PurpleBooth/game-of-life/archive/refs/tags/v1.31.0.tar.gz"
  sha256 "c05f34955bb193c84a28b6ce6396e53af7fe288189991eb2b5248ddce909ef41"

  depends_on "rust" => :build

  def install
    system "cargo", "install", "--locked", "--root", prefix, "--path", "."
  end

  test do
    system "#{bin}/game-of-life", "-h"
    system "#{bin}/game-of-life", "-V"
  end
end
EOF
git commit -am "Demonstration"

As a workaround you can return the default branch to master and it audit passes.

Output of brew config and brew doctor commands

$ brew config
HOMEBREW_VERSION: 2.3.0-71-g3a7213c
ORIGIN: https://github.com/Homebrew/brew
HEAD: 3a7213c2553da5a9022f82a746214ea255202ed0
Last commit: 6 hours ago
Core tap ORIGIN: https://github.com/Homebrew/homebrew-core
Core tap HEAD: 27684529432a5b5d7a86c7a0daf8f2a53de89412
Core tap last commit: 21 minutes ago
HOMEBREW_PREFIX: /usr/local
HOMEBREW_EDITOR: vim
HOMEBREW_MAKE_JOBS: 8
CPU: octa-core 64-bit haswell
Homebrew Ruby: 2.6.3 => /System/Library/Frameworks/Ruby.framework/Versions/2.6/usr/bin/ruby
Clang: 11.0 build 1103
Git: 2.27.0 => /usr/local/bin/git
Curl: 7.64.1 => /usr/bin/curl
Java: 14.0.1, 1.8.0_252
macOS: 10.15.4-x86_64
CLT: 11.5.0.0.1.1588476445
Xcode: N/A


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