chore: move flags to option package

[JeyJeyGao]

Moved internal/cmd/flags.go, internal/cmd/options.go and cmd/notation/common.go to option package to concentrate all the flags and options related code in one place.

[codecov]

Codecov Report

Attention: Patch coverage is 98.07692% with 1 line in your changes missing coverage. Please review.

Project coverage is 76.22%. Comparing base (1e5e342) to head (33e290e).

Files with missing lines	Patch %	Lines
cmd/notation/registry.go	80.00%	1 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #1195   +/-   ##
=======================================
  Coverage   76.22%   76.22%           
=======================================
  Files          71       70    -1     
  Lines        3634     3634           
=======================================
  Hits         2770     2770           
  Misses        668      668           
  Partials      196      196           

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

[shizhMSFT]

LGTM

[Two-Hearts]

Well... After reading through the PR, I personally prefer the previous structure, where internal/cmd/flags.go is clear enough for any developer to add a new flag in it.

From description at line 14: // Package cmd contains common flags and routines for all CLIs.
This description on package option leaves a deep concern, and my question is: Why do we have to keep creating new PRs to just move around internal files, renaming the package names with something else, while reducing readability of the code base and increasing developer mistakes like above? Is this really a MUST to do item?

[JeyJeyGao]

There are two issues in the repo:

1. Flags and options are located in multiple places: the internal/cmd package and cmd/notation/common.go.
2. The internal/cmd package name is too broad. What does cmd mean? Everything we are working on is command-related.

The option package only includes flags and options that are used when defining a command opts struct, so I think this name is a better choice.

[Two-Hearts]

As I mentioned in the above comment, your description to package option is already wrong, I'm pretty sure this is a reduction of readability and increases developing difficulty for others.

If you really want this chore PR, my suggestion is:
Move flag related code from common.go to internal/cmd/flags.go and that's it.