Manage DNS/bind9 zonefiles.

update:
    ./bin/update reads data from settings/, and generates zonefiles under zones/.

    `update` also shows and commits changes in settings/ data.

    -d DIR
        Do data operations under given dir-root, as opposed to CWD.

    -q
        Quiet. No log messages except errors.

    -vDV
        Increasing logging verbosity.

    -p
        Show diffs for changed output on stdout.

    -F
        Force-update output files, even if newer than input files.

    -S
        Do not generate new serials for zones.

    -s
        Generate new serials for all zones.

    -n
        Fake-update; show changes, but don't actually commit/deploy them.

        Useful for testing.

    -C
        Do not commit source changes.

    -c
        Force-commit source changes, even though -n

    -m MSG
        Commit message for source changes; optional

bin/update-serial:
    Increment DNS SOA record serials in the given .serial files.

    Uses a YYYYMMDDXX format, but supports XX overflow.

bin/process-zone:
    Read zonefile containing records, and generate any of:

    --check-hosts:
        Check for duplicate host names/IPs.

    --forward-zone:
        Generate additional TXT/MX records to supplement A/CNAME records.

    --reverse-zone=NET
        Generate PTR records for all matching A records.

    --meta-zone:
        Generate additional TXT records from zonefile metadata, read from:

            hg annotate -q --date | ./bin/process-zone --input-line-date ...

bin/expand-zone:
    Expand template vars in a zone textfile; does not parse records, just passes through lines.

    Used to substitute e.g. `--serial .../foo.serial` values into SOA '{serial}' fields.

bin/update:
    Runs update-serial/process-zone/expand-zone to keep various generated zones/views up-to-date with respect to
    source files under settings/.

    Also supports hg diff/commit/annotate integration with settings.

    Acts as our configuration file, determining the data/zones layout below.

settings/:
    Input files, fed through update to generate files under zones/

    *.serial:
        Zone serial numbers for corresponding *.zone

    *.zone:
        Zone header, passed through process-zone with `--serial *.serial` and any appropriate `--expand view=...`.

        May include a view-based $INCLUDE to include different zone data for different views.

    *.zone.*:
        Include zonefiles, $INCLUDE'd from *.zone

    *.txt:
        Hosts zone data, used to generate forwards/reverse -hosts zones

zones/:
    Output files, loaded by bind.

    common/*
        Common zone files shared across views.

    hosts/*:$view
        View-variant hosts zones generated from settings/*.txt

    hosts/*
        Host zones generated from settings/*.txt, may be used in some views but not others.

    includes/*:$view
        View-specific zone includes used from view/*.

    includes/*.*
        Zone includes used from view/*.

    $view/*
        Zone data for given zone/domain in given view

    $view/* -> ...:
        Symlinked generic-zone data for some specific zone; either to common/* or $view/*.