Warn when gitlab-shell version doesn't match requirement.

CHANGELOG

@@ -62,6 +62,7 @@ v 7.10.0 (unreleased)
   - Project labels are now available over the API under the "tag_list" field (Cristian Medina) 
   - Fixed link paths for HTTP and SSH on the admin project view (Jeremy Maziarz)
   - Fix and improve help rendering (Sullivan Sénéchal)
+  - Warn when gitlab-shell version doesn't match requirement.
 
 
 v 7.9.2

config/initializers/5_backend.rb

@@ -6,3 +6,10 @@
 
 # GitLab shell adapter
 require Rails.root.join("lib", "gitlab", "backend", "shell_adapter")
+
+required_version = Gitlab::VersionInfo.parse(Gitlab::Shell.version_required)
+current_version = Gitlab::VersionInfo.parse(Gitlab::Shell.new.version)
+
+unless current_version.valid? && required_version <= current_version
+  warn "WARNING: This version of GitLab depends on gitlab-shell #{required_version}, but you're running #{current_version}. Please update gitlab-shell."
+end

lib/gitlab/backend/shell.rb

@@ -240,7 +240,7 @@ def version
       gitlab_shell_version_file = "#{gitlab_shell_path}/VERSION"
 
       if File.readable?(gitlab_shell_version_file)
-        File.read(gitlab_shell_version_file)
+        File.read(gitlab_shell_version_file).chomp
       end
     end