tools: Fix changelog generation (again)

Using --first-parent --no-merges seems to exclude not just the merge
commits but all the commits from the merge as well. Let's use only
--no-merges to get just the commits without merges.

tools/fetch-distro.py

@@ -123,7 +123,7 @@ def update_distro(args, distro: str, config: dict):
         print(f'{pkg_subdir}: commit {new_commit!s} is still fresh')
         return
 
-    cmd = ['git', '-C', f'pkg/{pkg_subdir}', 'log', '--graph', '--first-parent',
+    cmd = ['git', '-C', f'pkg/{pkg_subdir}', 'log', '--graph', '--no-merges',
            '--pretty=oneline', '--no-decorate', '--abbrev-commit', '--abbrev=10',
            f'{old_commit}..{new_commit}']
     if subdir is not None:

tools/fetch-mkosi.py

@@ -75,7 +75,7 @@ def update_mkosi(args):
         print(f'mkosi: commit {new_commit!s} is still fresh')
         return
 
-    cmd = ['git', '-C', args.dir.as_posix(), 'log', '--graph', '--first-parent', '--no-merges',
+    cmd = ['git', '-C', args.dir.as_posix(), 'log', '--graph', '--no-merges',
            '--pretty=oneline', '--no-decorate', '--abbrev-commit', '--abbrev=10',
            f'{old_commit}..{new_commit}']
     print(f"+ {shlex.join(cmd)}")