Document fish_clipboard_copy/paste

doc_src/cmds/fish_clipboard_copy.rst

@@ -0,0 +1,36 @@
+.. _cmd-fish_clipboard_copy:
+
+fish_clipboard_copy - copy text to the system's clipboard
+==============================================================
+
+Synopsis
+--------
+
+.. synopsis::
+
+    fish_clipboard_copy
+
+    foo | fish_clipboard_copy
+
+Description
+-----------
+
+The ``fish_clipboard_copy`` function copies text to the system clipboard.
+
+If stdin is not a terminal (see :doc:`isatty <isatty>`), it will read all input from there and copy it. If it is, it will use the current commandline, or the current selection if there is one.
+
+It is bound to :kbd:`Control`\ +\ :kbd:`X` by default.
+
+``fish_clipboard_copy`` works by calling a system-specific backend. If it doesn't appear to work you may need to install yours.
+
+Currently supported are:
+
+- ``pbcopy``
+- ``wl-copy`` using wayland
+- ``xsel`` and ``xclip`` for X11
+- ``clip.exe`` on Windows.
+
+See also
+--------
+
+- :doc:`fish_clipboard_paste` which does the inverse.