feat: adjust generate cmd behavior according to latest discussion

[adohe]

What type of PR is this?

/kind feature

What this PR does / why we need it:

update generate cmd behavior according to latest discussion

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 8679211406

Details

• 4 of 54 (7.41%) changed or added relevant lines in 4 files are covered.
• 4 unchanged lines in 2 files lost coverage.
• Overall coverage increased (+0.05%) to 57.007%

---

Changes Missing Coverage	Covered Lines	Changed/Added Lines	%
pkg/cmd/generate/generator/generator.go	0	5	0.0%
pkg/cmd/generate/generate.go	2	47	4.26%

Files with Coverage Reduction	New Missed Lines	%
pkg/engine/operation/watch.go	1	85.93%
pkg/cmd/generate/generate.go	3	15.33%

Totals
Change from base Build 8656237463:	0.05%
Covered Lines:	7070
Relevant Lines:	12402

---

💛 - Coveralls

[elliotxx]

lgtm