autotag: add option for taking list of files from a text file.

Add an option for taking the list of input files from a text file:

  ./autotag -i files.txt

This is useful in conjunction with the `find` command:

  find ~/images/ -name '*.jpg' | ./autotag -i -

autotag

@@ -12,14 +12,23 @@ from more_itertools import ichunked
 @click.option("-n", "--limit", default=50, type=int, show_default=True, help="The maximum number of tags to return per image.")
 @click.option("-b", "--batch", "bs", default=128, type=int, show_default=True, help="The number of images to process per batch.")
 @click.option("-c", "--csv", is_flag=True, help="Output CSV instead of JSON.")
+@click.option("-i", "--input-file", type=click.File(), help="Read list of image filenames from text file.")
 @click.option("-g/-f", "--group-tags/--flatten-tags", default=True, show_default=True, help="Output rows in {filename, tags} format or {filename, tag, score} format.")
 @click.option("-N", "--name-only", is_flag=True, help="Output only the filename without the full path or extension.")
 @click.option("-m", "--model", default="models/model.pth", type=click.Path(exists=True), show_default=True, help="The model to use.")
-@click.argument("files", nargs=-1, type=click.Path(exists=True, allow_dash=True, path_type=Path), required=True)
-def main(files, threshold, limit, bs, csv, group_tags, name_only, model):
+@click.argument("files", nargs=-1, type=click.Path(exists=True, allow_dash=True, path_type=Path))
+def main(files, threshold, limit, bs, csv, input_file, group_tags, name_only, model):
     autotagger = Autotagger(model)
 
-    for filepaths in ichunked(get_filepaths(files), bs):
+    if input_file:
+        paths = (Path(line.rstrip()) for line in input_file)
+    elif len(files) > 0:
+        paths = get_filepaths(files)
+    else:
+        click.echo(click.get_current_context().get_help())
+        click.get_current_context().exit()
+
+    for filepaths in ichunked(paths, bs):
         filepaths = list(filepaths)
         files = [click.open_file(filepath, "rb") for filepath in filepaths]
         predictions = autotagger.predict(files, threshold=threshold, limit=limit, bs=bs)