core: add --keep-open, which doesn't close the file on EOF

The --keep-open option causes mpv not to close the current file.
Instead, it will pause, and allow the user to seek around. When
seeking beyond the end of the file, mpv does a precise seek back to
the previous last known position that produced video output.

In some corner cases, mpv might not be able to produce video output at
all, despite having created a VO. (Possibly when only 1 frame could be
decoded, but the video filter chain queues frames. Then a VO would be
created, without sending an actual video frame to the VO.) In these
cases, the VO window will not redraw, not even OSD.

Based on a patch by coax [1].

[1] http://devel.mplayer2.org/ticket/210#comment:4

1 files changed, 11 insertions, 0 deletions

diff --git a/DOCS/man/en/options.rst b/DOCS/man/en/options.rst
index e30de6a5a9..860c42f18c 100644
--- a/DOCS/man/en/options.rst
+++ b/DOCS/man/en/options.rst
@@ -877,6 +877,17 @@
     disable the window manager hints that force the window aspect ratio.
     (Ignored in fullscreen mode.)
 
+--keep-open
+    Do not terminate when playing or seeking beyond the end of the file.
+    Instead, pause the player. When trying to seek beyond end of the file, the
+    player will pause at an arbitrary playback position (or, in corner cases,
+    not redraw the window at all).
+
+    *NOTE*: this option is not respected when using ``--frames``, ``--end``,
+    ``--length``, or when passing a chapter range to ``--chapter``. Explicitly
+    skipping to the next file or skipping beyond the last chapter will terminate
+    playback as well, even if ``--keep-open`` is given.
+
 --key-fifo-size=<2-65000>
     Specify the size of the FIFO that buffers key events (default: 7). If it
     is too small some events may be lost. The main disadvantage of setting it