cleanup: directly use concurrent.futures instead of via pycompat
Python 2 is gone.
Differential Revision: https://phab.mercurial-scm.org/D12279
== New Features ==
* There is a new config section for templates used by hg commands. It
is called `[command-templates]`. Some existing config options have
been deprecated in favor of config options in the new
section. These are: `ui.logtemplate` to `command-templates.log`,
`ui.graphnodetemplate` to `command-templates.graphnode`,
`ui.mergemarkertemplate` to `command-templates.mergemarker`,
`ui.pre-merge-tool-output-template` to
`command-templates.pre-merge-tool-output`.
* There is a new set of config options for the template used for the
one-line commit summary displayed by various commands, such as `hg
rebase`. The main one is `command-templates.oneline-summary`. That
can be overridden per command with
`command-templates.oneline-summary.<command>`, where `<command>`
can be e.g. `rebase`. As part of this effort, the default format
from `hg rebase` was reorganized a bit.
* `hg purge` is now a core command using `--confirm` by default.
* `hg diff` and `hg extdiff` now support `--from <rev>` and `--to <rev>`
arguments as clearer alternatives to `-r <revs>`. `-r <revs>` has been
deprecated.
* The memory footprint per changeset during pull/unbundle
operations has been further reduced.
* There is a new internal merge tool called `internal:mergediff` (can
be set as the value for the `merge` config in the `[ui]`
section). It resolves merges the same was as `internal:merge` and
`internal:merge3`, but it shows conflicts differently. Instead of
showing 2 or 3 snapshots of the conflicting pieces of code, it
shows one snapshot and a diff. This may be useful when at least one
side of the conflict is similar to the base. The new marker style
is also supported by "premerge" as
`merge-tools.<tool>.premerge=keep-mergediff`.
* External hooks are now called with `HGPLAIN=1` preset. This has the side
effect of ignoring aliases, templates, revsetaliases, and a few other config
options in any `hg` command spawned by the hook. The previous behavior
can be restored by setting HGPLAINEXCEPT appropriately in the parent process.
See `hg help environment` for the list of items, and how to set it.
* The `branchmap` cache is updated more intelligently and can be
significantly faster for repositories with many branches and changesets.
* The `rev-branch-cache` is now updated incrementally whenever changesets
are added.
== New Experimental Features ==
* `experimental.single-head-per-branch:public-changes-only` can be used
restrict the single head check to public revision. This is useful for
overlay repository that have both a publishing and non-publishing view
of the same storage.
== Bug Fixes ==
== Backwards Compatibility Changes ==
* `--force-lock` and `--force-wlock` options on `hg debuglock` command are
renamed to `--force-free-lock` and `--force-free-wlock` respectively.
== Internal API Changes ==
* `changelog.branchinfo` is deprecated and will be removed after 5.8.
It is superseded by `changelogrevision.branchinfo`.