revlog: skip opener option to pass chunk_cache_size value We can directly set the option in the config object now.

revlog: create the revlog object at the repository level There is currently no value set in it, but we will be able to start centralise config parsing at the repository level.

revlog: overwrite revlog config through copy of the config object The new objects allow for this kind of blanket approach that make things cleaner. If we have more cases, it would probably deserve a context manager, but since we only have two usage, I don't think it is worth it.

revlog: move configuration attribute into dedicated object First this make things clearer as the number of configuration attributes has grown out of control, so gathering them make things clearer. Second, this will make future sharing them at different level simpler. Third it will allow us to make initialisation and temporary override simpler soon.

manifestrevlog: flag some inconsistency in bundle/union repo inheritance This "work" but still, this is weird, let us point it out.

randomaccessfile: drop explicit passing of file description The goal of this object is to manage IO, we still have to open the file if necessary, but this is all internal now.

revlog: drop more file description passing between private function They are no longer used as we are covered by the `reading` context

revlog: use a `reading` context in `_enforceinlinesize` We are about to enforce reading context on various operation, so we make sure top level method are in the right context. In the future we might move the responsibility of opening the revlog for reading higher in the call chain but lets limit the disruption for now.

revlog: drop the df argument to `sidedata` The intend of this argument is better filled by the `revlog.reading` or `revlog._writing` context. So we drop it to leave rooms for further cleanup and improvements.

revlog: drop the df argument to `rawdata` The intend of this argument is better filled by the `revlog.reading` or `revlog._writing` context. So we drop it to leave rooms for further cleanup and improvements.

revlog: drop the df argument to `revision` The intend of this argument is better filled by the `revlog.reading` or `revlog._writing` context. So we drop it to leave rooms for further cleanup and improvements.

interfaces: drop the `raw` parameters on ifiledata interface In practice it was not implemented since forever. The `rawdata` method fit that purpose. The interface checking does not detect that because it seems to confuse the `_df` argument for the `raw` one. Dropping that `_df` argument in a descendant changesets revealed the issue.

delta-computer: stop explicitly taking file handle The revlog has all the logic for opening and caching such handles, so no need to duplicate it here. In addition, this let the revlog handle that logic by itself which is better.

censors: simply use `revlog.reading` to keep things open dring rewrite We have a dedicated context now, we can simply use it. In practice, we cannot "simply" use it, as `finddeltainfo` still requires the file pointer to be passed explicitly. We will keep the old context manager open for a small bit until we get rid of it in a future changeset.

stream-clone: use `revlog.reading` in `revlog.get_streams` We can get the same result while using more standard method, so we do.

debug-revlog: keep the revlog open for the analysis duration This is more explicit. No performance differences were observed.

repo-upgrade: keep the revlog open while cloning This is more explicit. No performance differences were observed.

verify: keep the revlog open for reading while verifying it This is more explicit. No performances difference were observed.

convert: use `changelogrevision` to fetch changeset data instead of read This `changelogrevision` is a higher level function that will remain simple to use as we refactor the revlog.

revlog: adapt the `reading` check for `unionrepo` We cannot just rely on the length check for the `unionrepo` as the local revlog might be empty while the other revlog contains data. In addition, we need to also open the second revlog for reading when needed.

revlog: adapt the `reading` check for `bundlerepo` We cannot just rely on the length check for the `bundlerepo` as the local revlog might be empty with all data in the bundle.

revlog: make `reading` not crash on empty repository If the revlog is empty, the file might not exist and the open will fails. This is not great, but that details or this is now contained in the revlog itself.

changelog: make the `_delayopener` a real proxy We use the same approach as the `_divertopener`. This make it possible to use other methods of the vfs and not just the `__call__` API.

perf: ensure all readlog's reading is done within a `reading` context We are about to enforce this at the revlog level, so we update the perf code in advance.

perf: change the way we approach revlog reading If the `reading` context manager is available, we should use it over explicit file handle management. This will help us to make file handle management a matter more internal to the revlog.

revlog: document the `rev` method A small docstring does not hurt.

revlog: document the `clearcaches` method A small docstring does not hurt.

revlog: document the `update_caches` method A small docstring does not hurt.

revlog: make the `candelta` method private It is only used internally, so lets make it clear.

revlog: document the `get_streams` method A small docstring does not hurt.