docs: refresh cmd docs

[SparkYuan]

What type of PR is this?

/kind documentation

What this PR does / why we need it:

refresh cmd docs

Which issue(s) this PR fixes:

Fixes #

Special notes for your reviewer:

Does this PR introduce a user-facing change?

Additional documentation e.g., design docs, usage docs, etc.:

[coveralls]

Pull Request Test Coverage Report for Build 7043861862

• 21 of 21 (100.0%) changed or added relevant lines in 4 files are covered.
• 11 unchanged lines in 3 files lost coverage.
• Overall coverage decreased (-0.1%) to 74.948%

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Files with Coverage Reduction	New Missed Lines	%
pkg/engine/operation/watch.go	1	85.93%
pkg/engine/operation/parser/parser.go	3	79.27%
pkg/cmd/apply/options.go	7	71.83%

Totals
Change from base Build 7043528604:	-0.1%
Covered Lines:	6486
Relevant Lines:	8654

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💛 - Coveralls