stabletailgraph: extract _parents util func

stabletailgraph: clarify excl part size computation

stabletailgraph: clarify naiveness of current implementation Both the naive and the actual versions of the algorithms are going to co-exist for the tests. This makes is clearer that this one is naive.

stream-clone: introduce the notion of an experimental "v3" version We introduce a new experimental "v3" stream protocol, disabled by default. In practice the "v3-exp" protocol introduced in this changeset is identical to v2, but this changeset, lay the groundwork for having a new protocol: configuration, capability exchange, test coverage, etc. The actual protocol work will starts in the coming changesets.

stream-clone: check is a compatible protocol can be found The previous code was explicitly checking if "v2" is listed in the "stream" bundle2 capability. The new code is checking is there is anything common between the versions supported client side and server side overlaps. This prepare the introduction of more stream version than "v2".

stream-clone: bail-out earlier if stream clone is not requested The `canperformstreamclone` function is bit messy. However it seems clearer to me to check if a stream-clone have been requested by the client or the server at all, before checking if a compatible protocol can be negotiated with the server. So I am doing some gratuitous movement so reorder conditional.

stream-clone: bail-out earlier if pull is partial The `canperformstreamclone` function is bit messy. However it seems clearer to me to process the very generic condition about "can we consider a stream-clone at all", before checking if a stream-clone is requested and if a compatible protocol can be negotiated with the server. So I am doing some gratuitous movement so reorder conditional.

stream-clone: bail-out earlier if destination repo is not empty The `canperformstreamclone` function is bit messy. However it seems clearer to me to process the very generic condition about "can we consider a stream-clone at all", before checking if a stream-clone is requested and if a compatible protocol can be negotiated with the server. So I am doing some gratuitous movement so reorder conditional.

stream-clone: check the version of streaming clone supported by the client Make the server refuse to produce streaming clone bundle, if the client doesn't specify the stream=v2 capability. This is in preparation to introduce stream=v3. As far as I can tell, this capability was added at the same time as support for bundle2-based streaming pulls was added, so I don't expect clients to break. (the modern client doesn't break, at any rate)

stream-clone: make sure the `stream` capability is set when bundling This is important to start narrowing protocol option in the next changesets.

stream-clone: upgrade the error message for bad stream request The new version if more compact and more consistent with the general Mercurial usage.

stream-clone: yield cache entry in `_entries_walk` too The new function now cover the same ground as _v2_walk.

stream-clone: introduce a _entries_walk That function insert itself between the store and `_v2_walk`. It only deals with StoreEntry unlike `_v2_walk` that deal with actual file. A share of the `_v2_walk` logic will be moved in this new `_entry_walk` function. Having this function will help us to implement a new "v3" version of the protocol that will be more entry centric.

store: make `walk` return an entry for obsolescence if requested so Instead of having dedicated code in the streamclone code, we should have the store deal with advertising the data it contains.

store: yield phases before changelog Creating the `changelog.i` file make the repository usable, so dealing with phase earlier seems better.

store: make `walk` return an entry for phase if requested so Instead of having dedicated code in the streamclone code, we should have the store deal with advertising the data it contains.

cli: add a test of `hg debugnodemap --manifest` this is a new option that's not tested yet

cli: fix spelling in `debugnodemap` error messages

cli: make debugnodemap capable of inspecting an arbitrary nodemap This lets us inspect the manifest nodemap and individual directory nodemaps when treemanifest is used.

rust: mostly avoid streaming zstd decompression Streaming ZStd decompression seems slightly slower, and the API we use makes it very inconvenient to re-use the decompression context. Instead of using that, use the buffer-backed version, because we can give a reasonable-ish size estimate.

rust: in zstd decompression, avoid a useless vec initialization

rust: speed up zstd decompression by re-using the decompression context Admittedly, zstd is already pretty fast, but this change makes it a bit faster yet: it saves ~5% of time it takes to read our large repo. The actual motivating use case is treemanifest: in treemanifest we end up reading *lots* of small directories, and many of them need decompression, and there the saving for [rhg files] is >10%. (which also seems unreasonable, we should probably keep things uncompressed more)

store: rename `topfiles` to `top_entries` The method is now returning StoreEntries let us rename the method for clarity.

store: rename `datafiles` to `data_entries` The method is now returning StoreEntries let us rename the method for clarity.

store: use boolean property for upgrade's matchrevlog

store: use the new boolean property in `upgrade`

store: use the new boolean property in `remotefilelogserver`

store: use the boolean property in `repair_issue6528`

store: use the new boolean property in `narrow`

store: use the boolean property in `store`