input.conf: make explanatory text more readable

Or at leats this is the intention. It's a bit hard to tell which
information is needed, and which not.

DOCS/man/input.rst

@@ -4,6 +4,7 @@ INPUT.CONF
 The input.conf file consists of a list of key bindings, for example::
 
     s screenshot      # take a screenshot with the s key
+    LEFT seek 15      # map the left-arrow key to seeking forward by 15 seconds
 
 Each line maps a key to an input command. Keys are specified with their literal
 value (upper case if combined with ``Shift``), or a name for special keys. For

etc/input.conf

@@ -1,43 +1,29 @@
-# mpv input control file
+# mpv keybindings
 #
-# You are able to redefine default keyboard/joystick/mouse/LIRC bindings, or
-# add new ones here.
-# See DOCS/man/input.rst for possible commands that can be bound.
-# Also see mpv --input-cmdlist for other possible options.
-# The file should be placed in the $HOME/.config/mpv directory.
-#
-# mpv --input-test --force-window --idle can be used to test which commands
-# keys are bound to.
-#
-# If you wish to unbind a key, bind it to the 'ignore' command:
-#   KEY ignore
-#
-# Note that merely removing default key bindings from this file won't remove
-# the default bindings mpv was compiled with, unless
-#   --no-input-default-bindings
-# is specified.
+# Location of user-defined bindings: ~/.config/mpv/input.conf
 #
 # Lines starting with # are comments. Use SHARP to assign the # key.
+# Copy this file and uncomment and edit the bindings you want to change.
+#
+# List of commands and further details: DOCS/man/input.rst
+# List of special keys: --input-keylist
+# Keybindings testing mode: mpv --input-test --force-window --idle
+#
+# Use 'ignore' to unbind a key fully (e.g. 'ctrl+a ignore').
 #
 # Strings need to be quoted and escaped:
 #   KEY show_text "This is a single backslash: \\ and a quote: \" !"
 #
 # You can use modifier-key combinations like Shift+Left or Ctrl+Alt+x with
-# modifiers Shift, Ctrl, Alt and Meta, but note that currently reading
-# key combinations is only supported through the video windows of certain
-# output drivers (not in output windows of other drivers or in a terminal).
-
-# All lines in this file are commented. If you want to remap a key, copy the
-# file to ~/.config/mpv/input.conf, and uncomment and edit the binding you want
-# to change.
+# the modifiers Shift, Ctrl, Alt and Meta (may not work on the terminal).
+#
+# The default keybindings are hardcoded into the mpv binary.
+# You can disable them completely with: --no-input-default-bindings
 
 # Developer note:
-# etc/input.conf from the mpv source tree is baked into the mpv binary, with
-# all entries magically uncommented and parsed on initialization. Thus, this
-# file defines the mpv default key bindings. If this file is read as normal
-# config file, all lines starting with '#' are treated as comments (and this
-# file, if unedited, doesn't define any bindings).
-# Lines that have a space after the '#' are always ignored as real comments.
+# On compilation, this file is baked into the mpv binary, and all lines are
+# uncommented (unless '#' is followed by a space) - thus this file defines the
+# default key bindings.
 
 # If this is enabled, treat all the following bindings as default.
 #default-bindings start
@@ -112,7 +98,6 @@
 #d cycle framedrop                      # cycle through framedrop modes
 # toggle deinterlacer (automatically inserts or removes required filter)
 #D cycle deinterlace
-# Next 3 currently only work with --no-ass
 #r add sub-pos -1                       # move subtitles up
 #t add sub-pos +1                       #                down
 #v cycle sub-visibility