Only sync master branches when necessary

The server keeps track of library revisions now.
This means that we can check wether our local
clone is synced to the desired revision, and do so
if it isn't.

WARNING: dm:ci:client now syncs the master branches
of all datamapper gems. This means that you should
*never* do any work in master yourself (why would
you anyway?)

tasks.rb

@@ -465,7 +465,7 @@ def after
     def execute
       if executable?
         before
-        unless suppress_log?
+        unless suppress_log? || skip?
           log(command)
         end
         unless pretend?
@@ -625,6 +625,18 @@ def action
           'Pulling'
         end
 
+        def target_revision
+          env.options[:revision]
+        end
+
+        def revision
+          %x[git rev-parse head].chomp!
+        end
+
+        def skip?
+          target_revision == revision
+        end
+
       end
     end
 
@@ -826,6 +838,18 @@ def suppress_log?
         !executable? || print_matrix?
       end
 
+      def skip?
+        target_revision && !clean?
+      end
+
+      def target_revision
+        env.options[:revision]
+      end
+
+      def clean?
+        %x[git status] =~ /working directory clean/
+      end
+
     end
 
     class Gem < Rvm
@@ -956,15 +980,19 @@ class Job
         attr_reader :platform
         attr_reader :adapter
         attr_reader :library
+        attr_reader :revision
+        attr_reader :previous_status
 
         attr_reader :data
 
         def initialize(data, requested_status)
           @requested_status = requested_status
           @id               = data['id']
-          @platform         = data['platform']['name']
-          @adapter          = data['adapter' ]['name']
-          @library          = data['library' ]['name']
+          @platform         = data['platform_name']
+          @adapter          = data['adapter_name' ]
+          @library          = data['library_name' ]
+          @revision         = data['revision' ]
+          @previous_status  = data['previous_status' ]
           @data             = data
           @results          = {}
         end
@@ -996,28 +1024,29 @@ def accept
         end
 
         def execute
-          DataMapper::Project.sync(:include => [library], :rubies => [platform], :adapters => [adapter]) if upstream_modified?
-          DataMapper::Project.spec(:include => [library], :rubies => [platform], :adapters => [adapter])
+          permutation = { :include => [library], :rubies => [platform], :adapters => [adapter], :revision => revision }
+          DataMapper::Project.sync(permutation)
+          DataMapper::Project.spec(permutation)
         end
 
         def report
-          RestClient.post("#{CI::SERVICE_URL}/jobs/report", :report => { :job_id => self.id, :status => result })
+          RestClient.post("#{CI::SERVICE_URL}/jobs/report",
+            :report => {
+              :job_id   => self.id,
+              :status   => result,
+              :revision => revision
+            })
         end
 
         def running?
           @running
         end
 
-        def upstream_modified?
-          # TODO make this more solid with respect to 'skipped' (use SHA1s)
-          @requested_status.empty? || @requested_status.include?('modified')
-        end
-
         def result
           if @results[library]
             @results[library].first.to_s # we know that we only get one result back
           else
-            :skipped # HACK
+            'skipped' # HACK
           end
         end