[PATCH 1 of 2] amend: add noise in extra to avoid creating obsolescence cycle (issue3664)

[Kevin Bullock]

On Oct 18, 2012, at 11:03 AM, pierre-yves.david at logilab.fr wrote:

> # HG changeset patch
> # User Pierre-Yves David <pierre-yves.david at logilab.fr>
> # Date 1350575482 -7200
> # Node ID 122ab0793ce25a8ada0895fca25d05dbde7326a3
> # Parent  a1c4b21fc1b206f5cf386a8d9d5b5882aaa6807f
> amend: add noise in extra to avoid creating obsolescence cycle (issue3664)
> 
> Obsolescence cycle are bad and should be avoided as much as possible. The
> current amend implemented touch changeset meta data as few as possible. This
> make is easy for amend to result in the same node than a precursors. We add some
> deterministic noise in extra to avoid this. In practice, the hex of the amended
> changeset is stored in 'amend-from' extra key.
> 
> diff --git a/mercurial/cmdutil.py b/mercurial/cmdutil.py
> --- a/mercurial/cmdutil.py
> +++ b/mercurial/cmdutil.py
> @@ -1694,10 +1694,12 @@ def amend(ui, repo, commitfunc, old, ext
>                 user = opts.get('user') or old.user()
>                 date = opts.get('date') or old.date()
>             if not message:
>                 message = old.description()
> 
> +            extra['amend-from'] = old.hex()

Consistency with graft, transplant, and rebase would dictate that this key should be named 'amend_source'. At least switching to an underscore would be nice.

Other than that, LGTM.

pacem in terris / мир / शान्ति / ‎‫سَلاَم‬ / 平和
Kevin R. Bullock