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(You did create a GitHub account, didn't you? If not, see *New Developer Workflow.)
Clone from Origin Repository
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This creates a local working copy of the code that is independent of your personal fork.
Cloning Clone the repository (and specifying specify the "upstream repository") with the following commands:
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WARNING: Make sure to have any outstanding Pull Requests MERGED before deleting your personal fork, or your changes may get be lost.