download: now check tempfiles more carefully.

Now that gdown handles fully transferred files properly, by
ignoring them, the tempfile finder loop should only select files
ending with the right suffix (currently “(random).part”). This
avoids common situations where gdown finds the target file
itself, then tries to update it with a zero-byte partial transfer
in “--continue” mode.

Requiring a particular suffix also helps avoid a possible source
of file corruption when folders contain a lot of similarly named
files.

gdown/download.py

@@ -294,7 +294,7 @@ def download(
         # Alternatively, resume mode can reuse partial tmp_files.
         existing_tmp_files = []
         for file in os.listdir(osp.dirname(output) or "."):
-            if file.startswith(osp.basename(output)):
+            if file.startswith(osp.basename(output)) and file.endswith(TEMPFILE_SUFFIX):
                 existing_tmp_files.append(osp.join(osp.dirname(output), file))
         if resume and existing_tmp_files:
             if len(existing_tmp_files) != 1: