Validate: Add subjectWhitelist option, excepting specific subjects

[jzaefferer]

See the readme updats for usage details.

Fixes #26
Fixes #28

@scottgonzalez @mislav would be great if you could take a look at this

[scottgonzalez]

This seems ok, but this isn't really a whitelist, it's a required pattern.

[jzaefferer]

requiredPattern doesn't sound like an improvement. Could also be described as acceptable exceptions, but that doesn't make a good identifier either.

[mislav]

I guess configurability is useful, but if you as a project maintainer decide to configure this value and forget to explicitly bring in the fixup|squash bit, you would be inadvertently breaking these git features again for other committers. Since there is really no reason why would you ever want to de-whitelist these prefixes, I suggest that they're hardcoded somewhere instead of being configurable. The square bracket syntax could still be configurable and turned off at will.

[jzaefferer]

Thank you both for the feedback. I've now changed the approach, removing the option and instead hardcoding the accepted patterns. I can still make it configurable later, if the needs ever arises. For now I'm avoiding the naming and some other issues (can't put regex in JSON).

What do you think?

[mislav]

Yep,

[jzaefferer]

I've published this as part of 2.0.0 to npm.