+ def self.remote_url? repo_name
+ /^(https?|git):\/\// =~ repo_name
+ end
+
+ # Return [local_git_dir, is_remote]. If is_remote, caller must use
+ # fetch_remote_repository to ensure content is up-to-date.
+ #
+ # Raises an exception if the latest content could not be fetched for
+ # any reason.
+ def self.git_dir_for repo_name
+ if remote_url? repo_name
+ return [cache_dir_for(repo_name), true]
+ end
+ repos = Repository.readable_by(current_user).where(name: repo_name)
+ if repos.count == 0
+ raise ArgumentError.new "Repository not found: '#{repo_name}'"
+ elsif repos.count > 1
+ logger.error "Multiple repositories with name=='#{repo_name}'!"
+ raise ArgumentError.new "Name conflict"
+ else
+ return [repos.first.server_path, false]
+ end
+ end
+
+ def self.cache_dir_for git_url
+ File.join(cache_dir_base, Digest::SHA1.hexdigest(git_url) + ".git").to_s
+ end
+
+ def self.cache_dir_base
+ Rails.root.join 'tmp', 'git-cache'
+ end
+
+ def self.fetch_remote_repository gitdir, git_url
+ # Caller decides which protocols are worth using. This is just a
+ # safety check to ensure we never use urls like "--flag" or wander
+ # into git's hardlink features by using bare "/path/foo" instead
+ # of "file:///path/foo".
+ unless /^[a-z]+:\/\// =~ git_url
+ raise ArgumentError.new "invalid git url #{git_url}"
+ end
+ begin
+ must_git gitdir, "branch"
+ rescue GitError => e
+ raise unless /Not a git repository/ =~ e.to_s
+ # OK, this just means we need to create a blank cache repository
+ # before fetching.
+ FileUtils.mkdir_p gitdir
+ must_git gitdir, "init"
+ end
+ must_git(gitdir,
+ "fetch --no-progress --tags --prune --force --update-head-ok #{git_url.shellescape} 'refs/heads/*:refs/heads/*'")
+ end