Work with git submodules in nested folder structure.
[Fix #551] Replace -copy with copy-sequence
Merge pull request #552 from tuhdo/master

Update comment and use idiomatic method to build Helm source
Merge pull request #550 from no0/git-submodule-not-at-root-of-repo

Work with git submodules in nested folder structure.
Merge pull request #553 from tuhdo/master

Update helm-source-projectile-dired-files-list and fix bugs; update other sources