Read the gitlab-rails backup revision from a file

config/patches/gitlab-rails/backup_read_REVISION.patch

+diff --git a/lib/backup/manager.rb b/lib/backup/manager.rb
+index efaefa4..8f0e38f 100644
+--- a/lib/backup/manager.rb
++++ b/lib/backup/manager.rb
+@@ -7,7 +7,7 @@ module Backup
+       s = {}
+       s[:db_version]         = "#{ActiveRecord::Migrator.current_version}"
+       s[:backup_created_at]  = Time.now
+-      s[:gitlab_version]     = %x{git rev-parse HEAD}.gsub(/\n/,"")
++      s[:gitlab_version]     = File.read(Rails.root.join('REVISION')).chomp
+       s[:tar_version]        = %x{tar --version | head -1}.gsub(/\n/,"")
+ 
+       Dir.chdir(Gitlab.config.backup.path)
+@@ -92,7 +92,7 @@ module Backup
+         Dir.chdir(Rails.root)
+ 
+         # restoring mismatching backups can lead to unexpected problems
+-        if settings[:gitlab_version] != %x{git rev-parse HEAD}.gsub(/\n/, "")
++        if settings[:gitlab_version] != File.read(Rails.root.join('REVISION')).chomp
+           puts "GitLab version mismatch:".red
+           puts "  Your current HEAD differs from the HEAD in the backup!".red
+           puts "  Please switch to the following revision and try again:".red

config/software/gitlab-rails.rb

@@ -43,6 +43,8 @@ build do
   # source code to include the Git revision of the code included in the omnibus
   # build.
   command "sed -i \"s/.*REVISION.*/REVISION = '$(git log --pretty=format:'%h' -n 1)'/\" config/initializers/2_app.rb"
+  patch :source => "backup_read_REVISION.patch"
+  command "git rev-parse HEAD > REVISION"
   bundle "install --without mysql development test --path=#{install_dir}/embedded/service/gem", :env => env