Sumup in upstream release notes https://github.com/rpm-software-management/mock/wiki/Release-Notes-2.2

mock-2.2-1

• depend on mock-configs, not mock-core-configs so users can pick an alternative package with configuration
• bind-mounting stuff below /tmp into bootstrap is fixed with nspawn (GH#502)
• don't do util.getAddtlReqs when 'more_buildreqs' not specified
• implement doOutChroot() abstraction which runs commands either in bootstrap or on host, depending on isolation={nspawn|simple}
• use doOutChroot() for package_state plugin (GH#525)
• fix for "mock --chroot -- cmd arg1 arg2" use-case
• site-defaults.cfg moved from /etc to %%doc, and the config file is now provided by mock-core-configs (GH#555)
• bootstrap: expand dnf vars in local repo bind-mounts (#1815703)
• bootstrap: bindmount local metalink/mirrorlist (#1816696)
• config_opts['isolation'] option invented, replaces 'use_nspawn'
• 'isolation' is now set to 'auto' (means 'nspawn' with fallback to 'simple', (GH#337, otaylor@fishsoup.net)
• Fedora Toolbox && bootstrap - don't re-bind-mount dev files, and fix installation of filesystem.rpm from bootstrap to normal chroot (GH#550)
• re-define %%python3_pkgversion on el7 (GH#545)
• docker use-case: use getpass.getuser() instead of os.getlogin() (GH#551)
• set LANG to C.UTF-8 by default, even if host has different value (GH#451)
• bootstrap: use configured yum commands (GH#518, paul@city-fan.org)
• fixup doubled-logs by predictable bootstrap resultdir (GH#539, #1805631)
• fix --chain --isolation=simple with external URLs (GH#542)
• option --orphanskill fixed for --isolation=simple --bootstrap-chroot
• orphan processes are now also killed "postyum", right after the installation trasactions are executed to also kill daemons started from scriptlets (GH#183)
• EL7 fix - use 'private' mount option for <bootsrap_root>/<root>, not 'rprivate'
• ceanup rpmdb before checking installed packages (fixes builds against target chroots that have different rpmdb backend, e.g. SQLite on F33+)

mock-core-configs-32.6-1

• the site-defaults.cfg file moved from mock to mock-core-configs
• new option config_opts['isolation'], obsoletes 'use_nspawn'
• declare minimal version of mock, and set this to v2.2 as we use the new 'isolation' config option now, and we provide site-defaults.cfg file
• specify amazonlinux bootstrap image, to fix --use-bootstrap-image
• allow to replace mock-core-configs by packages that 'Provides: mock-configs'
• rpmlint: remove macro in comment