Accept filter instead of exclude mask for ignored fields

[jpbetz]

/sig api-machinery

kubernetes/kubernetes#128266 needs a way of expressing reset fields that can express "exclude all fields except for the container resource fields modifiable via /resize".

This provides a way to pass a filter instead of a field exclusion set.

[k8s-ci-robot]

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[AnishShah]

/lgtm

[k8s-ci-robot]

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/lgtm

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[jpbetz]

/assign @thockin
Do you have reviewer permissions in this repo? @AnishShah doesn't have /lgtm in this realm.

[thockin]

I don't think I do. I am trying to understand it and figure out how much I want to complain about the structure of it vs. accepting it as-is :)

[jpbetz]

I don't think I do. I am trying to understand it and figure out how much I want to complain about the structure of it vs. accepting it as-is :)

I don't mean to rush you. I'm thinking purely about the logistics of how to get a PR in this repo merged when it is ready. I'll hold to merge on your review.

[thockin]

I wrote and then deleted a dozen comments, as I understood it better on each reading. I did not review all the set logic, but looking at it for the ergonomics of defining patterns.

[jpbetz]

@thockin @AnishShah feedback applied.

[thockin]

LGTM, but I am not approver here. I understand the design, though.

For posterity, Joe and I discussed this in real time. He tells me it's fine and does not change SSA behavior:

Given input (indent for clarity only), which has exactly two "leaf" fields:

{
    "foo"                         /* struct */,
        "foo.bar"                 /* struct */,
            "foo.bar.bat"         /* struct */,
                "foo.bar.bat.qux" /* LEAF string */,
        "foo.zrb",                /* LEAF string */
}

Consider a strategy that has GetResetFields() => "foo.bar.bat". That would produce:

{
    "foo", "foo.bar", "foo.zrb"
    // note: "foo.bar.bat" and its children are culled
    // note: "foo.bar" remains, though it is empty
}

If we inverted it to an Include("foo.zrb"), that would produce:

{
    "foo", "foo.zrb"
    // note: only path elements leading to "foo.zrb" remain
}

In particular, note that "foo.bar" is absent. We didn't prune it from the old case, even though it is "empty". It didn't match anything in the new case.

In neither case did we match the "leaf" fields under "foo.bar.bat/*" (as expected).

[cici37]

/lgtm
/hold in case others wanna take a look.

[cici37]

nit: import sorting

[jpbetz]

/hold cancel