revlog: extract `deltainfo.distance` for future conditional redefinition This commit exist to make the next one clearer.

shelve: pick the most recent shelve if none specified for --patch/--stat Differential Revision: https://phab.mercurial-scm.org/D3950

shelve: improve help text for --patch and --stat It's not currently obvious why "hg shelve -p" fails, since -p doesn't take an argument. Differential Revision: https://phab.mercurial-scm.org/D3949

ssh: avoid reading beyond the end of stream when using compression Compressed streams can be used as part of getbundle. The normal read() operation of bufferedinputpipe will try to fulfill the request exactly and can deadlock if the server sends less as it is done. At the same time, the bundle2 logic will stop reading when it believes it has gotten all parts of the bundle, which can leave behind end of stream markers as used by bzip2 and zstd. To solve this, introduce a new optional unbufferedread interface and provided it in bufferedinputpipe and doublepipe. If there is buffered data left, it will be returned, otherwise it will issue a single read request and return whatever it obtains. Reorganize the decompression handlers to try harder to read until the end of stream, especially if the requested read can already be fulfilled. Check for end of stream is messy with Python 2, none of the standard compression modules properly exposes it. At least with zstd and bzip2, decompressing will remember EOS and fail for empty input after the EOS has been seen. For zlib, the only way to detect it with Python 2 is to duplicate the decompressobj and force some additional data into it. The common handler can be further optimized, but works as PoC. Differential Revision: https://phab.mercurial-scm.org/D3937

revset: add larger test for heads(ancestors(…)) It is important to not regress on this benchmark so we move it into the "base" file. And we add another benchmark with more than two revisions.

revset-benchmark: use a generic revset to test `heads(commonancestors())` This allow to benchmark revset performance in other repositories than just the mercurial one.

revlog: reintroduce `revlog.descendant` as deprecated Reintroduce `revlog.descendant` to help extensions authors update their extensions in order to use the new API.

context: reintroduce `ctx.descendant` as deprecated Reintroduce `ctx.descendant` to help extensions authors update their extensions in order to use the new API.

obsolete: explode if metadata contains invalid UTF-8 sequence (API) The current metadata API can be a source of bugs since it forces callers to process encoding conversion by themselves. So let's make it reject bad data as a last ditch. I assume there's no metadata field which is supposed to store arbitrary BLOB like transplant_source.

obsolete: store user name and note in UTF-8 (issue5754) (BC) Before, user names were stored in local encoding and transferred across repositories, which made it impossible to restore non-ASCII user names on different platforms. This patch fixes new markers to be encoded in UTF-8 and decoded back to local encoding when displaying. Existing markers are unfixable so they may result in mojibake. I don't like the API that requires metadata dict to be UTF-8 encoded, which is a source of bugs, but there's no abstraction layer to process the encoding thingy efficiently. So we apply the same rule as extras dict to obsstore metadata.