Feature: Move dotenv toward bash-like behavior

[motdotla]

Dotenv currently varies its behavior vs bash's behavior when sourcing .env files.

Consider moving toward behavior that will match bash.

Other discussions:

• fixes #439 #440
• Dotenv Should Allow Escaped Characters in Double Quoted Strings #496

should require a major version bump

[xzyfer]

Would "bash's behavior when sourcing .env files" also include supporting exported values (#112, #177, #213, and more)?

[devon-whil]

Is there any work around currently that allows the use of a dollar sign character?

[martin-braun]

@devon-whil KEY='asd$asd' works for me, but only if you choose to not expand the variables. If you expand the variables, you can use KEY="asd\$asd" just fine.

[phoenixeliot]

For anyone else having trouble with this: For an env variable that had to be JSON with interpolated string values, I had to do this non-bash-standard syntax:

SOME_VAR='["$INTERPOLATED_VAR","$OTHER_VAR"]'

This was in Next.js v12, which I think uses this package now. I know at some point they used their own custom thing, so not 100% sure about that.

[motdotla]

this effort will move into https://github.com/dotenvx/dotenvx (where a single consistent standard for .env file parsing is being developed across all languages and platforms)