tiup: add 3 docs mirror-init/mirror-rotate/cluster-patch (#5310)#5341

Merged

ti-chi-bot merged 1 commit intopingcap:release-4.0from ti-srebot:release-4.0-d1cf6dad3f46

Apr 15, 2021

Commits on Apr 15, 2021

cherry pick pingcap#5310 to release-4.0

CharLotteiu
authored and
ti-srebot
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