`--color` flag doesn't work anymore

[dvarrazzo]

In v3.9.2. --color doesn't force a coloured output anymore.

• In 2.8.1 a command such as helm diff upgrade NAME CHART --color | cat would show a coloured result.
• In 2.9.2 the output is monochrome.

If the output is direct to TTY, 2.9.2 produces a coloured output as well. It's the --color flag to force it to seem broken.

[yxxhero]

@dvarrazzo PR is welcome

[yxxhero]

#499 this PR breaks some flag checks. maybe we can only support --dry-run="***", and remove --dry-run? @mumoshu

[mumoshu]

@dvarrazzo Thanks for reporting! We're fixing that via #547.