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Video: Understand fast-forward merges

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Move a target branch to an existing descendant dark-palette commit without creating another commit. Contrast that fast-forward with a diverged input that must refuse.

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Video transcript

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  1. Start from the exact checkpoint.
  2. Name the branch, index and working version.
  3. Prepare only the isolated course copy.
  4. Start both branch names at the same commit.
  5. Record the real palette change.
  6. Return to the unchanged target.
  7. Confirm the merge direction.
  8. Require fast-forward only explicitly.
  9. Move the label to the existing descendant.
  10. Verify identities, not only graph shape.
  11. Preserve a diverged target instead of forcing it.
  12. What is required?
  13. Ancestry, not names or colors, determines fast-forward.
  14. What changes?
  15. The target moves to an existing D without a push.
  16. Resulting target SHA?
  17. The measured target equals the previous feature tip.
  18. Independent target commit added: ff-only?
  19. Divergence violates the required ancestry gate.
  20. Old M has two parents: proof this action merged?
  21. M's existing ancestry is not a new commit from this action.
  22. What proves completion?
  23. Both ref identity and file state are required.
  24. Verify the actual result, not just a message.
  25. Predict the changed input before acting.
  26. Preserve useful work before recovery.
  27. Prove the checkpoint before continuing.
  28. Keep the verified result for the next step.

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