repos.conf: default sync-webrsync-verify-signature

Enable sync-webrsync-verify-signature by default in repos.conf (due to
dependencies the ebuild will make this conditional on USE=rsync-verify
in the same way as the default sync-rsync-verify-metamanifest value).
Use a new PORTAGE_TEMP_GPG_DIR variable to distinguish indirect
emerge-webrsync calls that use gemato for secure key refresh, and
disable direct emerge-webrsync calls.

Deprecate FEATURES=webrsync-gpg and use it to trigger a
backward-compatibility mode where direct emerge-webrsync calls are
allowed (but trigger a warning message). Since direct emerge-webrsync
calls do not use gemato for secure key refresh, this behavior will
not be supported in a future release.

Bug: https://bugs.gentoo.org/689506
Signed-off-by: Zac Medico <zmedico@gentoo.org>
6 files changed