fix: Respect --frozen everywhere --offline or --locked is accepted

[epage]

What does this PR try to resolve?

Fixes #15239

This also makes --frozen be respected in more situations, including

• cargo add
• cargo install
• Git fetches
• HTTP registry access

How should we test and review this PR?

To prevent this from happening again, I removed offline() and locked() accessors. To maintain the quality of error messages, I added offline_flag() and locked_flag() that will pick up --frozen, if present.

Additional information

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[weihanglo]

This looks good. Thanks for the cleanup!

[weihanglo]

The change looks good, but we still have offline_flag and locked_flag here competing {network,lock_update}_allowed. They are not documented and might be misused again in the future.

What if we make *_allowed return an enum like these to avoid misuse, and can stop exposing *_flag method?

enum LockfileUpdate {
    Allowed,
    Disallowed(&'static str),
}

enum NetworkAccess {
    Allowed,
    Disallowed(&'static str),
}

[epage]

The *_flag functions are just like the bool functions, just with more data (and inverted). Not really seeing room for misuse like we had before.

As for an enum, while it makes it more explicit, it is also more cumbersome to use as you now need to access to the enum in each place you make the function call to compare the result. This also would encourage more of a match to make sure every case is handled when this is just a binary choice.

[weihanglo]

That is fair. Thanks for the explanation!