util: prefer "bytesio" to "stringio" The io.BytesIO and io.StringIO types enforce the type of data being operated on. On Python 2, we use cStringIO.StringIO(), which is lax about mixing types. On Python 3, we actually use io.BytesIO. Ideally, we'd use io.BytesIO on Python 2. But I believe its performance is poor compared to cString.StringIO(). Anyway, we canonically define our pycompat type as "stringio." That name is misleading, especially on Python 3. This commit renames the canonical symbols to "bytesio." "stringio" is preserved as an alias for API compatibility. There are a lot of callers in the repo and I hesitate to take away the old name. I also don't feel like changing everything at this time. But at least new callers can use a "proper" name. Differential Revision: https://phab.mercurial-scm.org/D2868

contrib: fix a subtle bug in check-code's regex rewriting We rewrite `\s` to `[ \t]` when preparing our regular expressions, but we previously weren't working to avoid having nested sets. Previously, Python let this slide without incident, but in Python 3.7 wants to make sure you meant an actual [ in a set, and so this warns. This appears to be fortunate for us, because `[\s(]` was getting rewritten to be `[[ \t](]` which doesn't actually match what we expected. See preceding changes that were revealed to be necessary after implementing this fix. Differential Revision: https://phab.mercurial-scm.org/D2866

remotenames: work around move of ABCs in collections This starts warning in Python 3.7, and will break in 3.8. The import is performed in a curious place because `import collections.abc` explodes badly on Python 2.7, and `from collections import abc` flunks our import checker. Differential Revision: https://phab.mercurial-scm.org/D2847

hgweb: explain instabilities of unstable changesets

debug: add debugwhyunstable that explains instabilities This is a port of evolve's feature of listing all unstable changesets in detail (`hg evolve --list`).

obsolete: move marker flags to obsutil Evolve extension expects to have obsolete.bumpedfix (imported in hgext3rd/evolve/evolvecmd.py), so we provide it.

debugupdatecache: also warm rev branch cache We add basic code to have `debugupdatecache` ensure that the rev branch cache is fully warmed. This only affects the `debugupdatecache` command, not normal transaction operation.