slskd appends "_<19-digit unix-nanosecond timestamp>" to a downloaded
filename when the destination already contains a same-named file
(concurrent downloads of the same track, partial-file retries after a
connection drop, cancelled-then-redownloaded files, the same track
surfacing in multiple synced playlists). The file-finder code already
recognized the suffix when matching a download to its source — but
after the canonical file moved into the library, the leftover
"_<timestamp>" siblings sat orphaned in the downloads folder forever.
Reported on Discord by Shdjfgatdif.
cleanup_slskd_dedup_siblings() runs at the end of each successful
import (3 safe_move_file sites in pipeline.py) and prunes any
remaining siblings that strip down to the canonical stem with the
same extension. Conservative match (>= 18 trailing digits) keeps
legitimate filenames like "Track 5" and "Album 1995" untouched. Per-
file unlink failures are swallowed so a single locked file doesn't
block the rest.
17 regression tests cover the suffix-strip primitive, orphan removal,
no-op cases, mismatched extensions, subdirectories, and partial-failure
recovery.