mkosi: Make MinimumVersion= a git commit

With the latest mkosi it's possible for MinimumVersion= to be a git
commit so let's start making use of that. This will make mkosi fail
if it's executed within the systemd repository and the checked out
commit is too old.

Putting the mkosi commit sha in mkosi/mkosi.conf also allows retrieving
it without having the full source tree available.

We also make a bunch of improvements to the fetch-mkosi.py script.

tools/fetch-distro.py

@@ -44,7 +44,7 @@ def read_config(distro: str):
 
 def commit_file(distro: str, files: list[Path], commit: str, changes: str):
     message = '\n'.join((
-        f'mkosi: update {distro} commit reference',
+        f'mkosi: update {distro} commit reference to {commit}',
         '',
         changes))
 

tools/fetch-mkosi.py

@@ -14,7 +14,8 @@ from pathlib import Path
 
 URL = 'https://github.com/systemd/mkosi'
 BRANCH = 'main'  # We only want to ever use commits on upstream 'main' branch
-FILENAME = Path('.github/workflows/mkosi.yml')
+CONFIG = Path('mkosi/mkosi.conf')
+WORKFLOWS = [Path('.github/workflows/mkosi.yml'), Path('.github/workflows/coverage.yml')]
 
 def parse_args():
     p = argparse.ArgumentParser(
@@ -32,29 +33,21 @@ def parse_args():
     return p.parse_args()
 
 def read_config():
-    print(f'Reading {FILENAME}…')
+    print(f'Reading {CONFIG}…')
     matches = [m.group(1)
-               for line in open(FILENAME)
-               if (m := re.match('^- uses: systemd/mkosi@([a-z0-9]{40})$',
+               for line in open(CONFIG)
+               if (m := re.match('^MinimumVersion=commit:([a-z0-9]{40})$',
                                  line.strip()))]
     assert len(matches) == 1
     return matches[0]
 
-def commit_file(args, file: Path, commit: str, changes: str):
-    cmd = [
-        'git', '-C', args.dir.as_posix(),
-        'describe',
-        '--always',
-        commit]
-    print(f"+ {shlex.join(cmd)}")
-    desc = subprocess.check_output(cmd, text=True).strip()
-
+def commit_file(files: list[Path], commit: str, changes: str):
     message = '\n'.join((
-        f'mkosi: update mkosi commit reference to {desc}',
+        f'mkosi: update mkosi commit reference to {commit}',
         '',
         changes))
 
-    cmd = ['git', 'commit', '-m', message, file.as_posix()]
+    cmd = ['git', 'commit', '-m', message, *(str(file) for file in files)]
     print(f"+ {shlex.join(cmd)}")
     subprocess.check_call(cmd)
 
@@ -88,13 +81,15 @@ def update_mkosi(args):
     print(f"+ {shlex.join(cmd)}")
     changes = subprocess.check_output(cmd, text=True).strip()
 
-    s = FILENAME.read_text()
-    assert old_commit in s
-    print(f'mkosi: {FILENAME}: found old hash, updating…')
-    new = s.replace(old_commit, new_commit)
-    assert new != s
-    FILENAME.write_text(new)
-    commit_file(args, FILENAME, new_commit, changes)
+    for f in [CONFIG, *WORKFLOWS]:
+        s = f.read_text()
+        assert old_commit in s
+        print(f'mkosi: {f}: found old hash, updating…')
+        new = s.replace(old_commit, new_commit)
+        assert new != s
+        f.write_text(new)
+
+    commit_file([CONFIG, *WORKFLOWS], new_commit, changes)
 
 if __name__ == '__main__':
     args = parse_args()