Re: [PATCH] log: use true parents for diff even when rewriting

> When using pathspec filtering in combination with diff-based log
> output, parent simplification happens before the diff is computed.
> The diff is therefore against the *simplified* parents.
>
> This works okay, arguably by accident, in the normal case: the pruned
> commits did not affect the paths being filtered, so the diff against
> the prune-result is the same as against the diff against the true
> parents.
>
> However, --full-diff breaks this guarantee, and indeed gives pretty
> spectacular results when comparing the output of
>
>   git log --graph --stat ...
>   git log --graph --full-diff --stat ...
>
> (--graph internally kicks in parent simplification, much like
> --parents).
>
> Reported-by: Uwe Kleine-König <u.kleine-koenig@pengutronix.de>
> Signed-off-by: Thomas Rast <trast@inf.ethz.ch>
> ---
>
> Perhaps like this.  It's getting a bit late, so I'm not sure if I'm
> missing another user of the "true" parent list, but it does fix the
> issue you reported.

> @@ -2820,6 +2821,7 @@ enum commit_action simplify_commit(struct rev_info *revs, struct commit *commit)
>  	if (action == commit_show &&
>  	    !revs->show_all &&
>  	    revs->prune && revs->dense && want_ancestry(revs)) {
> +		save_parents(commit);
>  		if (rewrite_parents(revs, commit, rewrite_one) < 0)
>  			return commit_error;
>  	}