command: extend subprocess command stdin, change behavior

Make it possible to feed a string to stdin of a subprocess. Out of
laziness, it can't be an arbitrary byte string. (Would require adding an
option type that takes in a Lua byte string.)

Do not set stdin of a subprocess to fd 0 (i.e. mpv's stdin) anymore,
because it makes things more consistent. Enabling stdin didn't make too
much sense in the first place, so this behavior change seems
justifiable.

win32 support missing.

Fixes: #8003

2 files changed, 14 insertions, 0 deletions

diff --git a/DOCS/interface-changes.rst b/DOCS/interface-changes.rst
index e58c13216d..bad810bef0 100644
--- a/DOCS/interface-changes.rst
+++ b/DOCS/interface-changes.rst
@@ -74,6 +74,9 @@ Interface changes
     - undeprecate --video-sync=display-adrop
     - deprecate legacy auto profiles (profiles starting with "extension." and
       "protocol."). Use conditional auto profiles instead.
+    - the "subprocess" command does not connect spawned processes' stdin to
+      mpv's stdin anymore. Instead, stdin is connected to /dev/null by default.
+      To get the old behavior, set the "passthrough_stdin" argument to true.
  --- mpv 0.32.0 ---
     - change behavior when using legacy option syntax with options that start
       with two dashes (``--`` instead of a ``-``). Now, using the recommended
diff --git a/DOCS/man/input.rst b/DOCS/man/input.rst
index 6213eb29fb..1be069306e 100644
--- a/DOCS/man/input.rst
+++ b/DOCS/man/input.rst
@@ -547,6 +547,17 @@ Remember to quote string arguments in input.conf (see `Flat command syntax`_).
         On Lua, you may use ``utils.get_env_list()`` to retrieve the current
         environment if you e.g. simply want to add a new variable.
 
+    ``stdin_data`` (``MPV_FORMAT_STRING``)
+        Feed the given string to the new process' stdin. Since this is a string,
+        you cannot pass arbitrary binary data. If the process terminates or
+        closes the pipe before all data is written, the remaining data is
+        silently discarded. Probably does not work on win32.
+
+    ``passthrough_stdin`` (``MPV_FORMAT_FLAG``)
+        If enabled, wire the new process' stdin to mpv's stdin (default: no).
+        Before mpv 0.33.0, this argument did not exist, but the default was if
+        it was set to ``yes``.
+
     The command returns the following result (as ``MPV_FORMAT_NODE_MAP``):
 
     ``status`` (``MPV_FORMAT_INT64``)