Add SCM module for Mercurial from Matthew Elder (closes #4150)

git-svn-id: http://svn.rubyonrails.org/rails/tools/capistrano@4830 5ecf4fe2-1ee6-0310-87b1-e25e094e27de

CHANGELOG

@@ -1,5 +1,7 @@
 *SVN*
 
+* Add SCM module for Mercurial (closes #4150) [Matthew Elder]
+
 * Remove unused line in SCM::Base (closes #5619) [chris@seagul.co.uk]
 
 * More efficient "svn log" usage (closes #5620) [Anatol Pomozov]

THANKS

@@ -1,3 +1,4 @@
 * Bazaar (v1) SCM Module: Edd Dumbill <edd@usefulinc.com>
 * Perforce SCM Module: Richard McMahon <richie.mcmahon@gmail.com>
-* Bazaar-NG SCM Module: Damien Merenne <dam@capsule.org>
+* Bazaar-NG SCM Module: Damien Merenne <dam@capsule.org>
+* Mercurial SCM Module: Matthew Elder <mae@mindflowsolutions.com>

lib/capistrano/scm/mercurial.rb

@@ -0,0 +1,83 @@
+require 'capistrano/scm/base'
+
+module Capistrano
+  module SCM
+
+    # An SCM module for using Mercurial as your source control tool.
+    # You can use it by placing the following line in your configuration:
+    #
+    #   set :scm, :mercurial
+    #
+    # Also, this module accepts a <tt>:mercurial</tt> configuration variable,
+    # which (if specified) will be used as the full path to the hg
+    # executable on the remote machine:
+    #
+    #   set :mercurial, "/usr/local/bin/hg"
+    class Mercurial < Base
+      # Return a string identifying the tip changeset in the mercurial
+      # repository. Note that this fetches the tip changeset from the
+      # local repository, but capistrano will deploy from your _remote_
+      # repository. So just make sure your local repository is synchronized
+      # with your remote one.
+      def latest_revision
+        `#{mercurial} tip --template '{node|short}'`
+      end
+
+      # Return the changeset currently deployed.
+      def current_revision(actor)
+        # NOTE:
+        # copied almost verbatim from svn except its not cast into an int
+        # this should be the same for almost _every_ scm can we take it out
+        # of SCM-specific code?
+        latest = actor.releases.last
+        grep = %(grep " #{latest}$" #{configuration.deploy_to}/revisions.log)
+        result = ""
+        actor.run(grep, :once => true) do |ch, str, out|
+          result << out if str == :out
+          raise "could not determine current changeset" if str == :err
+        end
+
+        date, time, user, changeset, dir = result.split
+        raise "current changeset not found in revisions.log" unless dir == latest
+        changeset
+      end
+
+      # Return a string containing the diff between the two changesets. +from+
+      # and +to+ may be in any format that mercurial recognizes as a valid 
+      # changeset. If +from+ is +nil+, it defaults to the last deployed
+      # changeset. If +to+ is +nil+, it defaults to the current working
+      # directory.
+      def diff(actor, from = current_revision(actor), to = nil)
+        cmd = "#{mercurial} diff -r #{from}"
+        cmd << " -r #{to}" if to
+        `#{cmd}`
+      end
+
+      # Check out (on all servers associated with the current task) the latest
+      # revision. Uses the given actor instance to execute the command. If
+      # mercurial asks for a password this will automatically provide it
+      # (assuming the requested password is the same as the password for
+      # logging into the remote server.) If ssh repository method is used,
+      # authorized keys must be setup.
+      def checkout(actor)
+        command = "#{mercurial} clone -U #{configuration.repository} " +
+                  "#{actor.release_path} && " +
+                  "#{mercurial} -R #{actor.release_path} update " +
+                   "-C #{configuration.revision} &&"
+        run_checkout(actor, command, &hg_stream_handler(actor)) 
+      end
+
+      private
+      def mercurial
+        configuration[:mercurial] || "hg"
+      end
+
+      def hg_stream_handler(actor)
+        Proc.new do |ch, stream, out|
+          prefix = "#{stream} :: #{ch[:host]}"
+          actor.logger.info out, prefix
+        end
+      end
+    end
+  end
+end