Add --only-photo/--only-video filters, skip NAS thumbnail dirs

Verified against real files pulled from are-nas: confirmed the tool
correctly leaves already-correct EXIF-dated photos untouched and only
flags the ones actually missing real metadata (validates the earlier
manual fix was precisely targeted). Recursive --dir walk now prunes
@eaDir/#recycle/#snapshot/.SynologyWorkingDirectory instead of wasting
time on generated thumbnails. Fixed a misleading "no files given"
error when --dir was given but --only-photo/--only-video filtered
everything out.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

set_mtime_from_metadata.py

@@ -39,6 +39,8 @@ Usage:
     ./set_mtime_from_metadata.py --dry-run *.mov
     ./set_mtime_from_metadata.py --dir /path/to/library          # recursive, prompts before applying
     ./set_mtime_from_metadata.py --dir /path/to/library --yes    # recursive, unattended
+    ./set_mtime_from_metadata.py --dir /path/to/library --only-photo --dry-run
+    ./set_mtime_from_metadata.py --dir /path/to/library --only-video --yes
 
 Requirements:
     - ffprobe on PATH (for .mov/.mp4/.m4v)
@@ -57,8 +59,14 @@ QUICKTIME_TAG_PRIORITY = ["com.apple.quicktime.creationdate", "creation_time"]
 
 QUICKTIME_EXTS = {".mov", ".mp4", ".m4v"}
 AVI_EXTS = {".avi"}
+VIDEO_EXTS = QUICKTIME_EXTS | AVI_EXTS
 EXIF_PHOTO_EXTS = {".jpg", ".jpeg", ".png", ".tif", ".tiff", ".heic", ".heif"}
-ALL_SUPPORTED_EXTS = QUICKTIME_EXTS | AVI_EXTS | EXIF_PHOTO_EXTS
+ALL_SUPPORTED_EXTS = VIDEO_EXTS | EXIF_PHOTO_EXTS
+
+# Synology (and other NAS/sync tool) internal housekeeping directories that
+# only ever contain generated thumbnails/cache, never real source media --
+# pruned from --dir's recursive walk so they don't show up as noisy skips.
+SKIP_DIR_NAMES = {"@eaDir", "#recycle", "#snapshot", ".SynologyWorkingDirectory"}
 
 # Reject anything dated before this as a clock-never-set placeholder rather
 # than a real timestamp (observed in the wild: "0000:00:00 00:00:00").
@@ -155,10 +163,11 @@ def fetch_creation_time(path):
     return None
 
 
-def iter_batch_files(root):
-    for dirpath, _dirnames, filenames in os.walk(root):
+def iter_batch_files(root, allowed_exts):
+    for dirpath, dirnames, filenames in os.walk(root):
+        dirnames[:] = [d for d in dirnames if d not in SKIP_DIR_NAMES]
         for name in filenames:
-            if Path(name).suffix.lower() in ALL_SUPPORTED_EXTS:
+            if Path(name).suffix.lower() in allowed_exts:
                 yield Path(dirpath) / name
 
 
@@ -180,22 +189,39 @@ def main():
     parser = argparse.ArgumentParser(description=__doc__, formatter_class=argparse.RawDescriptionHelpFormatter)
     parser.add_argument("files", nargs="*", type=Path, help="Media files to fix")
     parser.add_argument("--dir", type=Path, help="Recursively scan this directory for supported files instead of (or in addition to) explicit FILES")
+    type_group = parser.add_mutually_exclusive_group()
+    type_group.add_argument("--only-photo", action="store_true", help="Only consider photo formats (jpg/jpeg/png/tif/tiff/heic/heif)")
+    type_group.add_argument("--only-video", action="store_true", help="Only consider video formats (mov/mp4/m4v/avi)")
     parser.add_argument("--dry-run", action="store_true", help="Show what would change without modifying anything or prompting")
     parser.add_argument("--yes", "-y", "--unattended", dest="yes", action="store_true", help="Apply changes without an interactive confirmation prompt")
     args = parser.parse_args()
 
-    targets = list(args.files)
+    if not args.files and not args.dir:
+        parser.error("no files given -- pass FILES and/or --dir")
+
+    allowed_exts = EXIF_PHOTO_EXTS if args.only_photo else VIDEO_EXTS if args.only_video else ALL_SUPPORTED_EXTS
+
+    targets = []
+    excluded_by_type = []
+    for f in args.files:
+        if f.suffix.lower() not in allowed_exts:
+            excluded_by_type.append((f, "excluded by --only-photo/--only-video"))
+            continue
+        targets.append(f)
     if args.dir:
         if not args.dir.is_dir():
             print(f"error: --dir {args.dir}: not a directory", file=sys.stderr)
             sys.exit(2)
-        targets.extend(sorted(iter_batch_files(args.dir)))
+        targets.extend(sorted(iter_batch_files(args.dir, allowed_exts)))
     if not targets:
-        parser.error("no files given -- pass FILES and/or --dir")
+        for f, err in excluded_by_type:
+            print(f"skip: {f}: {err}", file=sys.stderr)
+        print("nothing to do: no files matched (check --only-photo/--only-video and the extensions under --dir)", file=sys.stderr)
+        sys.exit(1 if excluded_by_type else 0)
 
     plans = [plan_for(f) for f in targets]
     ok_plans = [(p, dt) for p, dt, err in plans if err is None]
-    skipped = [(p, err) for p, dt, err in plans if err is not None]
+    skipped = excluded_by_type + [(p, err) for p, dt, err in plans if err is not None]
 
     for p, err in skipped:
         print(f"skip: {p}: {err}", file=sys.stderr)