Fix broken -f option on single files instead of directories

main.py

@@ -1,8 +1,11 @@
 #!/usr/bin/env python3
+# pylint: disable=consider-using-with
+# (this code contains some IO stream juggling)
 from sys import stdin
 from sys import exit as sysexit
 from io import BytesIO
 from subprocess import Popen, PIPE
+from pathlib import Path
 
 import click
 from blake3 import blake3
@@ -42,7 +45,7 @@ def get_input_stream(kwargs):
     if (text := kwargs["text"]) is not None:
         stream = ClosableStream(BytesIO(text.encode()))
     elif file := kwargs["file"]:
-        stream = get_deterministic_tar_stream(file)
+        stream = get_deterministic_stream(file)
     elif not stdin.isatty():
         stream = ClosableStream(stdin.buffer)
     return stream
@@ -57,8 +60,15 @@ class ClosableStream:
         return self._close_func()
 
 
+def get_deterministic_stream(file):
+    if Path(file).is_dir():
+        return get_deterministic_tar_stream(file)
+
+    ifile = open(file, 'rb')
+    return ClosableStream(ifile, ifile.close)
+
+
 def get_deterministic_tar_stream(file):
-    # pylint: disable=consider-using-with
     cmd = (
         'tar',
         f'--blocking-factor={BUF_SIZE//512}',