add usage docs

bin/breplay_stream.py

@@ -1,4 +1,21 @@
 #!/usr/bin/python3
+#
+# Replay a stream, as if mitmproxy were sending filter requests via the filter/apply API
+#
+# Usage:
+#
+#  breplay_stream.py path_prefix
+#
+#      path_prefix  : some file prefix
+#
+# This will list all files matching the prefix, sort them, and play them back.
+# These files should come in triplets: a .url file, a .headers.json file, and a .data file/
+#
+# To capture requests for later playback:
+#   * Set debug_stream_fqdn and debug_stream_uri in mitmproxy/bubble_config.py and restart mitmproxy servers
+#   * Request a matching using a device whose traffic will be routed through the mitmproxy
+#   * Capture files will be written to /tmp/bubble_stream_[request-id]_chunkXXXX.[url, headers.json, data]
+#
 import glob
 import json
 import requests