Use the tests-passed branch when upgrading Discourse for stability.

app/controllers/docker_manager/admin_controller.rb

@@ -15,7 +15,7 @@ module DockerManager
         repos << DockerManager::GitRepo.new(File.dirname(p.path), p.name)
       end
       repos.map! do |r|
-        result = {name: r.name, path: r.path }
+        result = {name: r.name, path: r.path, branch: r.branch }
         if r.valid?
           result[:id] = r.name.downcase.gsub(/[^a-z]/, '_').gsub(/_+/, '_').sub(/_$/, '')
           result[:version] = r.latest_local_commit

lib/docker_manager/git_repo.rb

@@ -1,11 +1,14 @@
 # like Grit just very very minimal
 class DockerManager::GitRepo
-  attr_reader :path, :name
+  attr_reader :path, :name, :branch
 
   def initialize(path, name=nil)
     @path = path
     @name = name
     @memoize = {}
+
+    # For discourse proper, defauilt to the `tests-passed` branch
+    @branch = (path == Rails.root.to_s) ? 'tests-passed' : 'master'
   end
 
   def start_upgrading
@@ -74,7 +77,10 @@ class DockerManager::GitRepo
   end
 
   def tracking_branch
-    run "for-each-ref --format='%(upstream:short)' $(git symbolic-ref -q HEAD)"
+    return @tracking_branch if @tracking_branch
+    @tracking_branch = run("for-each-ref --format='%(upstream:short)' $(git symbolic-ref -q HEAD)")
+    @tracking_branch.gsub!('master', branch)
+    @tracking_branch
   end
 
   def run(cmd)

lib/docker_manager/upgrader.rb

@@ -20,7 +20,7 @@ class DockerManager::Upgrader
 
     # HEAD@{upstream} is just a fancy way how to say origin/master (in normal case)
     # see http://stackoverflow.com/a/12699604/84283
-    run("cd #{@repo.path} && git fetch && git reset --hard HEAD@{upstream}")
+    run("cd #{@repo.path} && git fetch && git checkout #{@repo.branch} && git reset --hard HEAD@{upstream}")
     log("********************************************************")
     log("*** Please be patient, next steps might take a while ***")
     log("********************************************************")