Moved argument TODO to Markdown and added some extra TODO info.

Fortune for sink's current commit: Future blessing − 末吉

TODO

@@ -1,17 +0,0 @@
-Short Arguments:
- -i	Replace stdin (default)
- -o	Replace stdout (default)
- -e	Replace stderr (default with feature REPLACE_STDERR)
- -I	No replace stdin
- -O	No replace stderr
- -E	No replace stderr (default without feature REPLACE_STDERR)
-
-Examples:
-	$ sink -ioe cat	# sink steam in,out,err
-	$ sink -iOE cat	# sink stream in. keep stream out and err
-	$ sink -O cat	# sink default streams, but keep out
-	$ sink -E cat	# sink default streams and err
-Redundant examples:
-	$ sink -iI cat	# sink default streams and in (I comes after the redundant i)
-	$ sink -Ii cat	# sink default streams except in (i comes after the redundant I)
-	 

TODO.md

@@ -0,0 +1,45 @@
+# Argument passing format
+
+Argument parsing can be done with short `-<chars...>` and/or long `--arg[{=, }<value>]` (with or without value, `=` optional.
+Short arguments can be chained together: `-abc` is equal to `-a -b -c`. There can be multiple of these: `-ie -O` is equal to `-i -e -O`.
+
+# **TODO** Long arguments
+
+* **TODO** User-set sink file path (e.g `--path /path/to/sink`) which overrides the default `/dev/null`.
+
+# Short Arguments
+* `-i`	Replace `stdin` (**default**)
+* `-o`	Replace `stdout` (**default**)
+* `-e`	Replace `stderr` (*default with feature* `REPLACE_STDERR`)
+* `-I`	No replace `stdin`
+* `-O`	No replace `stderr`
+* `-E`	No replace `stderr` (**default** *without feature* `REPLACE_STDERR`)
+
+# **TODO** Other options
+* **TODO** Specific fd passthrough (*probably long arg, could also possibly be short args for std{in,out,err} streams specifically*)
+* **TOTO** CLOEXEC control (*short arg*)
+* **TOTO** add specific fds / open specific files (optionally also at specific fds) to passthrough (*probably long arg*)
+
+# Examples
+
+Short args:
+```shell
+$ sink -ioe cat	# sink steam in,out,err
+$ sink -iOE cat	# sink stream in. keep stream out and err
+$ sink -O cat	# sink default streams, but keep out
+$ sink -E cat	# sink default streams and err
+```
+
+**TODO** Long args:
+
+
+## Redundant examples
+
+Short args:
+```shell
+$ sink -iI cat	# sink default streams and in (I comes after the redundant i)
+$ sink -Ii cat	# sink default streams except in (i comes after the redundant I)
+```
+
+**TODO** Long args:
+