scripts: add versionary.py to drive FCOS versioning

This script implements the versioning scheme as described in:
coreos/fedora-coreos-tracker#211

The next step is to use this in the FCOS pipeline to drive versioning.

scripts/versionary.py

@@ -0,0 +1,140 @@
+#!/usr/bin/python3 -u
+
+'''
+    Implements the Fedora CoreOS versioning scheme as per:
+        https://github.com/coreos/fedora-coreos-tracker/issues/81
+        https://github.com/coreos/fedora-coreos-tracker/issues/211
+'''
+
+import argparse
+import json
+import os
+import re
+import subprocess
+import sys
+import time
+import yaml
+
+from datetime import datetime
+
+
+def main():
+    args = parse_args()
+    if args.workdir is not None:
+        os.chdir(args.workdir)
+    assert os.path.isfile('builds/builds.json'), 'Missing builds/builds.json!'
+
+    x, y, z = (get_x(), get_y(), get_z())
+    n = get_next_iteration(x, y, z)
+    new_version = f'{x}.{y}.{z}.{n}'
+
+    # sanity check the new version by trying to re-parse it
+    assert parse_version(new_version) is not None
+    print(new_version)
+
+
+def parse_args():
+    parser = argparse.ArgumentParser()
+    parser.add_argument('--workdir', help="path to cosa workdir")
+    return parser.parse_args()
+
+
+def get_x():
+    """
+        X is the Fedora release version on which we're based.
+    """
+    manifest = get_flattened_manifest()
+    releasever = manifest['releasever']
+    eprint(f"Got releasever {releasever} from manifest")
+    return int(releasever)
+
+
+def get_y():
+    """
+        Y is the base snapshot date in YYYYMMDD format of Fedora. We derive
+        this using the timestamp in the base lockfile.
+    """
+    # XXX: should sanity check that the lockfiles for all the basearches have
+    # matching timestamps
+    with open('src/config/manifest-lock.x86_64.json') as f:
+        lockfile = json.load(f)
+    generated = lockfile.get('metadata', {}).get('generated')
+    if not generated:
+        raise Exception(f"Missing 'metadata.generated' key from {lockfile}")
+    dt = datetime.strptime(generated, '%Y-%m-%dT%H:%M:%SZ')
+    ymd = dt.strftime('%Y%m%d')
+    eprint(f"Got lockfile timestamp {ymd}")
+    return int(ymd)
+
+
+def get_z():
+    """
+        Z is the stream indicator.
+    """
+    # https://github.com/coreos/fedora-coreos-tracker/issues/211#issuecomment-543547587
+    stream_to_int = {
+        'next': 1,
+        'testing': 2,
+        'stable': 3,
+        'next-devel': 10,
+        'testing-devel': 20,
+        'rawhide': 91,
+        'branched': 92,
+        'bodhi-updates-testing': 93,
+        'bodhi-updates': 94,
+    }
+    manifest = get_flattened_manifest()
+    stream = manifest['add-commit-metadata']['fedora-coreos.stream']
+    eprint(f"Got stream {stream} from manifest")
+    assert stream in stream_to_int, f"Unknown stream: {stream}"
+    mapped = stream_to_int[stream]
+    eprint(f"Mapped stream {stream} to {mapped}")
+    return mapped
+
+
+def get_next_iteration(x, y, z):
+    with open('builds/builds.json') as f:
+        builds = json.load(f)
+
+    if len(builds['builds']) == 0:
+        eprint(f"No previous builds")
+        return 0
+
+    last_buildid = builds['builds'][0]['id']
+    last_version = parse_version(last_buildid)
+    if not last_version:
+        eprint(f"Previous version {last_buildid} does not match scheme")
+        return 0
+
+    if (x, y, z) != last_version[:3]:
+        eprint(f"Previous version {last_buildid} x.y.z does not match")
+        return 0
+
+    return last_version[3] + 1
+
+
+def get_flattened_manifest():
+    return yaml.safe_load(
+        subprocess.check_output(['rpm-ostree', 'compose', 'tree', '--repo',
+                                 'tmp/repo', '--print-only',
+                                 'src/config/manifest.yaml']))
+
+
+def parse_version(version):
+    m = re.match(r'^([0-9]{2})\.([0-9]{8})\.([0-9]+)\.([0-9]+)$', version)
+    if m is None:
+        return None
+    # sanity-check date
+    try:
+        time.strptime(m.group(2), '%Y%m%d')
+    except ValueError:
+        return None
+    return tuple(map(int, m.groups()))
+
+
+def eprint(*args):
+    print(*args, file=sys.stderr)
+
+
+if __name__ == "__main__":
+    sys.exit(main())