* Improve make_playlist.py code quality and fix bugs
- Fix group name bug: replace underscores with spaces before title()
so filenames like north_korea.md produce "North Korea" not "North_Korea"
- Fix resource leaks: use context managers for all file handles including
EPG list and per-country playlist files
- Remove os.chdir() global side effect: use absolute paths derived from
the script location instead
- Avoid calling to_m3u_line() twice per channel by caching the result
- Fix redundant trailing colon in filename[:-3:] slice
- Consistent use of write() for headers instead of mixing print/write
- Strip blank lines from EPG URL list when reading
* Skip commit and push when playlist has no changes
Prevents the workflow from failing with exit code 1 when the generated
playlist is identical to the previous run and there is nothing to commit.
* Use current branch instead of hardcoded master for push
Replace hardcoded origin/master reference with @{u} (upstream of current
branch) for the diff check, and use HEAD for the push target so the
workflow works correctly on any branch.
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Co-authored-by: Kálmán „KAMI” Szalai <kami911gmail.com>