Refactor the main logic.

[lijunle]

• Calculate the unused dependencies to the end of the flow.
• Concatenate the deps and devDeps at the beginning of the flow.
• Some minor changes.
• Preparation for the missing dependencies feature.

[codecov-io]

Current coverage is 98.45%

Merging #89 into master will increase coverage by +0.30% as of c162460

@@            master     #89   diff @@
======================================
  Files           15      15       
  Stmts          325     323     -2
  Branches        75      75       
  Methods          0       0       
======================================
- Hit            319     318     -1
+ Partial          4       3     -1
  Missed           2       2       

Review entire Coverage Diff as of c162460

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