tests: fix test-chg to ignore a warning about being unable to set locale This is apparently coming from bash when bash is providing the sh that we're using to execute the .sh file generated by run-tests for this test. Bash on my machine: ``` $ sh --version GNU bash, version 5.1.4(1)-release (x86_64-pc-linux-gnu) Copyright (C) 2020 Free Software Foundation, Inc. License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html> This is free software; you are free to change and redistribute it. There is NO WARRANTY, to the extent permitted by law. $ sh sh-5.1$ LC_CTYPE=unsupported_value echo hi sh: warning: setlocale: LC_CTYPE: cannot change locale (unsupported_value): No such file or directory hi ``` Differential Revision: https://phab.mercurial-scm.org/D10468

branch: delete obsolete message about changing branch of obsolete commit We now rely on `rewriteutil.precheck()` to check for divergence, so we don't need the extra check in `cmdutil.changebranch()`. The former check is a little less strict in that it allows you to rewrite a commit without non-obsolete successors. Differential Revision: https://phab.mercurial-scm.org/D10519

rewriteutil: check for divergence This code is adapted from the code in the evolve extension. It seems to be equivalent as far as the evolve extension's test suite can tell (the only impact when making their `precheck()` delegate to our version is that error messages are less detailed). I had to change the error message to work with "change branch of" being inserted as the action. Differential Revision: https://phab.mercurial-scm.org/D10518

rewriteutil: adapt "cannot %s while merging" to work with "change branch of" `rewriteutil.precheck()` creates error messages by inserting a given verb into a sentence. The `hg branch -r` command passes in "change branch of" as the verb. That doesn't work well with "cannot %s while merging" (making it "cannot change branch of while merging"). Let's insert a "changeset" there to make it work better. Building sentences like this seems obviously bad for i18n, but fixing that is out of scope for this series, IMO. Differential Revision: https://phab.mercurial-scm.org/D10530

rewriteutil: point to help about instability when rewriting creates orphan This replicates the message from the evolve extension. Differential Revision: https://phab.mercurial-scm.org/D10517

help: add topic about evolution, based on text from evolve extension I've taken the text produced by `hg help evolution` when the evolve extension is enabled and made that available by the same command with just hg core. Changes I've made: * Added "(EXPERIMENTAL)" to the title. (That doesn't hide the topic from `hg help`, though.) * Replaced old-style `experimental.evolution=<names>` config by new-style `experimental.evolution.<name>=true`. * Replaces a "obsolete markers" by "obsolescence markers". * Removed most content from "Current feature status". When the evolve extension is enabled, its help text takes precedence. Differential Revision: https://phab.mercurial-scm.org/D10516

rewriteutil: add devel warning if precheck is called with contexts I'm trying to upstream parts from the evolve extension. This check exists there. Differential Revision: https://phab.mercurial-scm.org/D10515

rewriteutil: replace "null changeset" by "the null revision" in error message The evolve extension uses "the null revision" and we seem to use that term much more frequently in core too. Differential Revision: https://phab.mercurial-scm.org/D10514

node: replace nullid and friends with nodeconstants class The introduction of 256bit hashes require changes to nullid and other constant magic values. Start pushing them down from repository and revlog where sensible. Differential Revision: https://phab.mercurial-scm.org/D9465

Added signature for changeset 411dc27fd9fd

Added tag 5.8.1 for changeset 411dc27fd9fd

corruption: backout changeset 49fd21f32695 (issue6528) inverting the parent is masking copy information leading to bad content being fetched and bad status result. Since 49fd21f32695, exchange can actively swap these parent corrupting existing changesets and triggering the corruption. Data corruption are considered critical so backing this out and doing and unscheduled release seems in order. Differential Revision: https://phab.mercurial-scm.org/D10995

corruption: add a test for issue6528 The initial reproduction script was provided by Charles Chamberlain from Jane Street. Differential Revision: https://phab.mercurial-scm.org/D10996

stream: double check that self.vfs is *not* in the vfsmap The stream clone logic allows for writing any content to any file under various vfs. This is *not* suitable for *vfs*, since writing in `.hg/` directly allow to modify the configuration and is a great and simple gateway for remote code execution. Differential Revision: https://phab.mercurial-scm.org/D10905