manpage: minor fixes

- The video filter to turn the video upside-down is vflip. There is no
  filter called "flip" so using it just causes an error.
- Reword a sentence.
- Add exact and all to the values accepted by cover-art-auto. They were
  implemented in 029ff1049b but not added to the accepted arguments.

DOCS/man/input.rst

@@ -912,7 +912,7 @@ Input Commands that are Possibly Subject to Change
 
     .. admonition:: Example for input.conf
 
-        - ``a vf set flip`` turn video upside-down on the ``a`` key
+        - ``a vf set vflip`` turn the video upside-down on the ``a`` key
         - ``b vf set ""`` remove all video filters on ``b``
         - ``c vf toggle gradfun`` toggle debanding on ``c``
 
@@ -3420,8 +3420,8 @@ caveats with some properties (due to historical reasons):
     the initial filter chain cannot be created.
 
     This behavior changed in mpv 0.31.0. Before this, the new value was rejected
-    *iff* video (for ``vf``) or audio (for ``af``) was active. If playback was
-    not active, the behavior was the same as the current behavior.
+    *iff* a video (for ``vf``) or an audio (for ``af``) track was active. If
+    playback was not active, the behavior was the same as the current one.
 
 ``playlist``
     The property is read-only and returns the current internal playlist. The

DOCS/man/options.rst

@@ -6737,7 +6737,7 @@ Miscellaneous
     CLI/config file only alias for ``--cover-art-files-append``. Each use of this
     option will add a new external file.
 
-``--cover-art-auto=<no|fuzzy>``
+``--cover-art-auto=<no|exact|fuzzy|all>``
     Whether to load _external_ cover art automatically. Similar to
     ``--sub-auto`` and ``--audio-file-auto``. If a video already has tracks
     (which are not marked as cover art), external cover art will not be loaded.