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-u, --sysupgrade
Upgrades all packages that are out-of-date. Each currently-installed package will be examined and upgraded if a newer package exists. A
report of all packages to upgrade will be presented, and the operation will not proceed without user confirmation. Dependencies are
automatically resolved at this level and will be installed/upgraded if necessary.
Pass this option twice to enable package downgrades; in this case, pacman will select sync packages whose versions do not match with the
local versions. This can be useful when the user switches from a testing repository to a stable one.
Additional targets can also be specified manually, so that -Su foo will do a system upgrade and install/upgrade the "foo" package in the
same operation.