manifest: proxy to revlog instance instead of inheriting Previously, manifestrevlog inherited revlog.revlog and therefore exposed all its APIs. This inevitably resulted in consumers calling low-level revlog APIs. As part of abstracting storage, we want to formalize the interface for manifest storage. The revlog API is much too large to define as the interface. Like we did for filelog, this commit divorces the manifest class from revlog so that we can standardize on a smaller API surface. The way I went about this commit was I broke the inheritance, ran tests, and added proxies until all tests passed. Like filelog, there are a handful of attributes that don't belong on the interface. And like filelog, we'll tease these out in the future. As part of this, we formalize an interface for manifest storage and add checks that manifestrevlog conforms to the interface. Adding proxies will introduce some overhead due to extra attribute lookups and function calls. On the mozilla-unified repository: $ hg verify before: real 627.220 secs (user 525.870+0.000 sys 18.800+0.000) after: real 628.930 secs (user 532.050+0.000 sys 18.320+0.000) $ hg serve (for a clone) before: user 223.580+0.000 sys 14.270+0.000 after: user 227.720+0.000 sys 13.920+0.000 $ hg clone before: user 506.390+0.000 sys 29.720+0.000 after: user 513.080+0.000 sys 28.280+0.000 There appears to be some overhead here. But it appears to be 1-2%. I think that is an appropriate price to pay for storage abstraction, which will eventually let us have much nicer things. If the overhead is noticed in other operations (whose CPU time isn't likely dwarfed by fulltext resolution) or if we want to cut down on the overhead, we could dynamically build up a type whose methods are effectively aliased to a revlog instance's. I'm inclined to punt on that problem for now. We may have to do it for the changelog. At which point it could be implemented in a generic way and ported to filelog and manifestrevlog easily enough I would think. .. api:: manifest.manifestrevlog no longer inherits from revlog The manifestrevlog class now wraps a revlog instance instead of inheriting from revlog. Various attributes and methods on instances are no longer available. Differential Revision: https://phab.mercurial-scm.org/D4386