Code review comment for lp:~vila/bzr/374726-gc-annotate

This pach fixes the most blatant regression for any gc repository. Whether the repository is packed or not doesn't matter anymore.

There is still a performance regression compared to knit repositories but far more limited (at most 2x) and related to gc different choices for deltas (leading to different reannotate intermediate calls, the same annotations being finally produced anyway).

Since we are not satisfied with annotate performance in either case, I'd like some feedback about whether it's worth spending time on trying to catch up with knit here (inverstigating with jam showed no obvious way to achieve that though) or go for implementing an annotation cache (which is out of this bug scope).