linux/update-mainline: fix -rc version spelling, clean up a bit

#!/usr/bin/env nix-shell

#!nix-shell -i python3 -p "python3.withPackages (ps: [ ps.beautifulsoup4 ps.lxml ps.packaging ])"

from functools import cached_property

from itertools import groupby

import json

import os

class KernelRelease:

    nature: KernelNature

    version: str

    branch: str

    date: str

    link: str

    eol: bool = False

    @cached_property

    def parsed_version(self) -> Version:

        return parse_version(self.version)

    @cached_property

    def branch(self) -> str:

        version = self.parsed_version

        # This is a testing kernel.

        if version.is_prerelease:

            return "testing"

        else:

            return f"{version.major}.{version.minor}"

def parse_release(release: Tag) -> KernelRelease | None:

    columns: list[Tag] = list(release.find_all("td"))

    try:

        nature = KernelNature[columns[0].get_text().rstrip(":").upper()]

    except KeyError:

        # skip linux-next

        return None

    version = parse_version(columns[1].get_text().rstrip(" [EOL]"))

    version = columns[1].get_text().rstrip(" [EOL]")

    date = columns[2].get_text()

    link = columns[3].find("a")

    if link is not None and isinstance(link, Tag):

    return KernelRelease(

        nature=nature,

        branch=get_branch(version),

        version=version,

        date=date,

        link=link,

    )

def get_branch(version: Version):

    # This is a testing kernel.

    if version.is_prerelease:

        return "testing"

    else:

        return f"{version.major}.{version.minor}"

def get_hash(kernel: KernelRelease):

    if kernel.branch == "testing":

        args = ["--unpack"]

        sys.exit(1)

    releases = release_table.find_all("tr")

    parsed_releases = filter(None, [parse_release(release) for release in releases])

    parsed_releases = [

        parsed for release in releases

        if (parsed := parse_release(release)) is not None

    ]

    all_kernels = json.load(VERSIONS_FILE.open())

    oldest_branch = get_oldest_branch()

    for (branch, kernels) in groupby(parsed_releases, lambda kernel: get_branch(kernel.version)):

        kernel = max(kernels, key=lambda kernel: kernel.version)

    for (branch, kernels) in groupby(parsed_releases, lambda kernel: kernel.branch):

        kernel = max(kernels, key=lambda kernel: kernel.parsed_version)

        nixpkgs_branch = branch.replace(".", "_")

        old_version = parse_version(all_kernels.get(branch, {}).get("version"))

        old_version = all_kernels.get(branch, {}).get("version")

        if old_version == kernel.version:

            print(f"linux_{nixpkgs_branch}: {kernel.version} is latest, skipping...")

            continue

        print(message, file=sys.stderr)

        all_kernels[branch] = {

            "version": str(kernel.version),

            "version": kernel.version,

            "hash": get_hash(kernel),

        }