Improvements to brew versions

The output happens as it is determined, rather than all at once, which is preferable for CLI commands. This meant I had to hard-code the left-justification.

The pre-amble warning is removed. Instead the command outputs the git checkout command for each she that you can type to get that old formula.

I decided that reseting the one file will work 99% of the time and that it is too risky to reset the whole repo, this will roll-back bug fixes. Instead we should add functionality to compat/ in order to support old formula as required. Sometimes deps may have to be rolled-back too, but the user will have to figure this out on an ad-hoc basis. We are assuming a failure sophisticated user anyway, one who would like to get old versions of stuff.

I moved most of the functions into Formula since IMO this makes more conceptual sense.

I made the she get abbreviated by git (using --abbrev-commit) itself so it as short as can be.

Library/Homebrew/cmd/versions.rb

@@ -3,89 +3,64 @@ require 'formula'
 module Homebrew extend self
 
   module Versions
-
+    # yields version, sha for all versions in the git history
-    # The commit SHA for a specific version of a formula
+    def self.old_versions f
-    def self.sha_for name, version
+      yielded = []
-      shas_for(name).each do |sha|
+      f.rev_list.each do |sha|
-        return sha if version == version_for(name, sha)
+        version = f.version_for_sha sha
-      end
+        unless yielded.include? version
-
+          yield version, sha
-      nil
+          yielded << version
-    end
-
-    # All SHAs of the commits the named formula has been changed in
-    def self.shas_for name
-      `git --git-dir=#{HOMEBREW_REPOSITORY}/.git rev-list HEAD^ -- Library/Formula/#{name}.rb`.split
-    end
-
-    # Returns the version number for the named formula and the given commit SHA
-    def self.version_for name, sha
-      code = `git --git-dir=#{HOMEBREW_REPOSITORY}/.git show #{sha}:Library/Formula/#{name}.rb`
-      version = code.match(/class #{Formula.class_s name} < ?Formula.*?(?:version\s|@version\s*=)\s*(?:'|")(.+?)(?:'|").*?end\s/m)
-      if version.nil?
-        url = code.match(/class #{Formula.class_s name} < ?Formula.*?(?:url\s|@url\s*=)\s*(?:'|")(.+?)(?:'|").*?end\s/m)
-        if url.nil?
-          head = code.match(/class #{Formula.class_s name} < ?Formula.*?head\s'(.*?)'.*?end\s\s/m)
-          if head.nil?
-            opoo "Version of #{name} could not be determined for #{sha}."
-            nil
-          else
-            'HEAD'
-          end
-        else
-          Pathname.new(url[1]).version
-        end
-      else
-        version[1]
-      end
-    end
-
-    # All older versions of a formula together with the SHA of their most recent
-    # revision
-    def self.old_versions(formula)
-      old_versions = []
-
-      shas_for(formula.name).each do |sha|
-        old_version = version_for formula.name, sha
-
-        if old_version != formula.version &&
-           (old_versions.empty? || old_version != old_versions.last[0])
-          old_versions << [old_version, sha]
         end
       end
-
-      old_versions
     end
-
   end
 
   def versions
-    puts "Listing older versions for: #{ARGV.formulae.join(', ')}"
+    raise "Please `brew install git` first" unless system "/usr/bin/which -s git"
-
-    puts <<-EOS.undent
-
-      If you want to install one of these old versions run `git reset --hard
-      $COMMIT_ID_OF_VERSION` in "#{HOMEBREW_REPOSITORY}". After that you can install the formula
-      like usual with `brew install formula`. When you're done use `git reset --hard
-      master@{1}` in "#{HOMEBREW_REPOSITORY}" to get back to the most recent versions again.
-
-      WARNING: This also reverts Homebrew itself to an old revision. This may lead to
-      broken installations and/or not being able to install an old formula at all.
-    EOS
 
     ARGV.formulae.all? do |f|
-      old_versions = Versions.old_versions f
+      old_versions = Versions.old_versions f do |version, sha|
-
+        print Tty.white
-      if old_versions.empty?
+        print "#{version.ljust(8)} "
-        puts "\nThere are no older versions for \"#{f.name}\" (current: #{f.version})."
+        print Tty.reset
-      else
+        puts "git checkout #{sha} #{HOMEBREW_REPOSITORY}/Library/Formula/#{name}.rb"
-        puts "\nOlder versions for \"#{f.name}\" (current: #{f.version}):\n"
-
-        max_size = 0
-        old_versions.each { |v| max_size = v[0].size if v[0].size > max_size }
-        old_versions.each { |v| puts '  %s (%s)' % [v[0].ljust(max_size), v[1]] }
       end
     end
   end
 
 end
+
+
+class Formula
+  def rev_list
+    Dir.chdir HOMEBREW_REPOSITORY do
+      `git rev-list --abbrev-commit HEAD Library/Formula/#{name}.rb`.split
+    end
+  end
+
+  def sha_for_version version
+    revlist.find{ |sha| version == version_for(sha) }
+  end
+
+  def version_for_sha sha
+    # TODO really we should open a new ruby instance and parse the formula
+    # class and then get the version but this would be too slow (?)
+
+    code = Dir.chdir(HOMEBREW_REPOSITORY) do
+      `git show #{sha}:Library/Formula/#{name}.rb`
+    end
+
+    version = code.match(/class #{Formula.class_s name} < ?Formula.*?(?:version\s|@version\s*=)\s*(?:'|")(.+?)(?:'|").*?end\s/m)
+    return version[1] unless version.nil?
+
+    url = code.match(/class #{Formula.class_s name} < ?Formula.*?(?:url\s|@url\s*=)\s*(?:'|")(.+?)(?:'|").*?end\s/m)
+    return Pathname.new(url[1]).version unless url.nil?
+
+    head = code.match(/class #{Formula.class_s name} < ?Formula.*?head\s'(.*?)'.*?end\s\s/m)
+    return 'HEAD' unless head.nil?
+
+    opoo "Version of #{name} could not be determined for #{sha}."
+  end
+
+end