brew-audit is inconsistent regarding depends_on "git"

[bfontaine]

To reproduce this issue, create a Library/Formula/test.rb file:

class Test < Formula
  homepage "http://www.example.com"
  url "http://www.example.com/foo"
  version "0.1.0"
  sha256 "9b25a4c8e12d6703627ba24f4547a7d4350ca1ef9fa44415512b1bcc57b06506"

  depends_on "git"

  def install
  end

  test do
    system "true"
  end
end

Then run brew audit --strict test:

1 file inspected, no offenses detected

==> audit problems
test:
 * Use `depends_on :git` instead of `depends_on 'git'`

Error: 1 problems in 1 formulae

Now fix the audit problem:

depends_on :git

And re-audit:

Error: Unsupported special dependency :git
Please report this bug:
    https://git.io/brew-troubleshooting
/usr/local/Library/Homebrew/dependency_collector.rb:136:in `parse_symbol_spec'
/usr/local/Library/Homebrew/dependency_collector.rb:81:in `parse_spec'
/usr/local/Library/Homebrew/dependency_collector.rb:65:in `build'
/usr/local/Library/Homebrew/dependency_collector.rb:48:in `block in fetch'
/usr/local/Library/Homebrew/dependency_collector.rb:48:in `fetch'
/usr/local/Library/Homebrew/dependency_collector.rb:48:in `fetch'
/usr/local/Library/Homebrew/dependency_collector.rb:38:in `add'
/usr/local/Library/Homebrew/software_spec.rb:128:in `depends_on'
/usr/local/Library/Homebrew/formula.rb:923:in `block in depends_on'
/usr/local/Library/Homebrew/formula.rb:923:in `each'
/usr/local/Library/Homebrew/formula.rb:923:in `depends_on'
/usr/local/Library/Formula/test.rb:7:in `<class:Test>'
/usr/local/Library/Formula/test.rb:1:in `load_file'
/usr/local/Library/Homebrew/formulary.rb:92:in `module_eval'
/usr/local/Library/Homebrew/formulary.rb:92:in `load_file'
/usr/local/Library/Homebrew/formulary.rb:82:in `klass'
/usr/local/Library/Homebrew/formulary.rb:71:in `get_formula'
/usr/local/Library/Homebrew/formulary.rb:200:in `factory'
/usr/local/Library/Homebrew/extend/ARGV.rb:16:in `block in formulae'
/usr/local/Library/Homebrew/extend/ARGV.rb:16:in `map'
/usr/local/Library/Homebrew/extend/ARGV.rb:16:in `formulae'
/usr/local/Library/Homebrew/cmd/audit.rb:12:in `audit'
/usr/local/Library/brew.rb:135:in `<main>'

---

$ brew doctor
Your system is ready to brew.
$ brew config
HOMEBREW_VERSION: 0.9.5
ORIGIN: https://github.com/Homebrew/homebrew.git
HEAD: 01dd3e19f8e600c3f44a3b140103f330aa32447c
Last commit: 2 hours ago
HOMEBREW_PREFIX: /usr/local
HOMEBREW_CELLAR: /usr/local/Cellar
CPU: quad-core 64-bit haswell
OS X: 10.10.2-x86_64
Xcode: 6.2
CLT: 6.2.0.0.1.1424975374
Clang: 6.0 build 600
X11: 2.7.7 => /opt/X11
System Ruby: 2.0.0-p481
Perl: /usr/bin/perl
Python: /usr/local/bin/python => /usr/local/Cellar/python/2.7.9/Frameworks/Python.framework/Versions/2.7/bin/python2.7
Ruby: /Users/baptiste/.rvm/rubies/ruby-2.1.0/bin/ruby
Java: 1.7.0_40

[jacknagel]

Yeah, the advice is wrong, we never list git as a dependency and there is no :git dependency.

[xu-cheng]

There is a GitDependency. But we fail to associate it with :git.

[MikeMcQuaid]

We should instead tell people to just not depend on git.

[MikeMcQuaid]

(as it is always installed)