$ brew versions leiningen
1.7.1    git checkout 78de146 /usr/local/Library/Formula/leiningen.rb
1.7.0    git checkout 38651b4 /usr/local/Library/Formula/leiningen.rb
1.6.2    git checkout 6b29b2b /usr/local/Library/Formula/leiningen.rb
1.6.1.1  git checkout 8bf90f2 /usr/local/Library/Formula/leiningen.rb
1.6.1    git checkout 8c7871b /usr/local/Library/Formula/leiningen.rb
1.6.0    git checkout 7a4c16d /usr/local/Library/Formula/leiningen.rb
1.5.2    git checkout 2b1b4e1 /usr/local/Library/Formula/leiningen.rb
1.5.0    git checkout f2e2af7 /usr/local/Library/Formula/leiningen.rb
1.4.2    git checkout 0476235 /usr/local/Library/Formula/leiningen.rb
1.4.1    git checkout f248101 /usr/local/Library/Formula/leiningen.rb
1.4.0    git checkout f74c3b4 /usr/local/Library/Formula/leiningen.rb
1.3.1    git checkout 7871a99 /usr/local/Library/Formula/leiningen.rb
1.3.0    git checkout bdf93f9 /usr/local/Library/Formula/leiningen.rb
1.2.0    git checkout a907ece /usr/local/Library/Formula/leiningen.rb
1.1.0    git checkout b178a73 /usr/local/Library/Formula/leiningen.rb
1.0.1    git checkout ec4906b /usr/local/Library/Formula/leiningen.rb
0.5.0    git checkout f375c3d /usr/local/Library/Formula/leiningen.rb
$ cd /usr/local
$ git co 8bf90f2 /usr/local/Library/Formula/leiningen.rb
$ brew install leiningen

つまり:

  1. brew version leiningen で取得可能なバージョンを調査
  2. /usr/local へ移動して目的のFormulaをチェックアウト
  3. install