Update git submodules
Update git submodules

* Update plugins/download-commands from branch 'master'
  to 5c50f9b17e616fd84d2c561822161fff46bbf902
  - Refactor repo commands
    
    We've had a single "repo command" stuffed in the download UI which
    doesn't make a lot of sense.  The command types are more about how
    they mutate your local checkout, not the commands used to download.
    
    Lets merge the repo-vs-git logic into GitDownloadCommand directly.
    We create separate "getRepoCommand" and "getCommand" methods for
    downstream classes to extend with the default "getRepoCommand"
    defaulting to null.
    
    Bug: Issue 11594
    Change-Id: I6848c431975ec4db3aa09a160af5198b93ce5bb9
    
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