amend: use an explicit commit message for temporary amending commit Before this changeset, the extra commit created during amend had the same description as the final commit. This was a bit confusing when trying to understand what that extra commit was about. This changeset changes the description of such commit to: temporary amend commit for <ammend-commit-hash> The old behaviour was not a big deal, but would become more confusing once we use obsolescence marker instead of stripping the precursors. This also helps if the user restores a strip backup.