revlog: avoid calculating "flags" twice in revision() This is more consistent with other code in "revision()" - prefer performance to code length.

revlog: use raw revision for rawsize When writing the revlog-ng index, the third field is len(rawtext). See revlog._addrevision: textlen = len(rawtext) .... e = (offset_type(offset, flags), l, textlen, base, link, p1r, p2r, node) self.index.insert(-1, e) Therefore, revlog.index[rev][2] returned by revlog.rawsize should be len(rawtext), where "rawtext" is revlog.revision(raw=True). Unfortunately it's hard to add a test for this code path because "if l >= 0" catches most cases.

revsetlang: enable optimization of 'x + y' expression It's been disabled since 4d1e56b29a91, but it can be enabled now as the ordering requirement is resolved at analyze().

repair: use rawvfs when copying extra store files If we use the normal vfs, store encoding will be applied when we .join() the path to be copied. This results in attempting to copy a file that (likely) doesn't exist. Using the rawvfs operates on the raw file path, which is returned by vfs.readdir(). Users at Mozilla are encountering this, as I've instructed them to run `hg debugupgraderepo` to upgrade to generaldelta. While Mercurial shouldn't deposit any files under .hg/store that require encoding, it is possible for e.g. .DS_Store files to be created by the operating system.

tests: add test demonstrating buggy path handling `hg debugupgraderepo` is currently buggy with regards to path handling when copying files in .hg/store/. Specifically, it applies the store filename encoding to paths instead of operating on raw files. This commit adds a test demonstrating the buggy behavior.

repair: iterate store files deterministically An upcoming test will add a 2nd file. Since readdir() is non-deterministic, add a sorted() to make traversal deterministic.

zstd: vendor python-zstandard 0.8.0 Commit 81e1f5bbf1fc54808649562d3ed829730765c540 from https://github.com/indygreg/python-zstandard is imported without modifications (other than removing unwanted files). Updates relevant to Mercurial include: * Support for multi-threaded compression (we can use this for bundle and wire protocol compression). * APIs for batch compression and decompression operations using multiple threads and optimal memory allocation mechanism. (Can be useful for revlog perf improvements.) * A ``BufferWithSegments`` type that models a single memory buffer containing N discrete items of known lengths. This type can be used for very efficient 0-copy data operations. # no-check-commit