fish_vi_cursor: add new variable for external cursor mode (#9565)

* add new variable for external cursor mode

* fix backwards compatibility

* add documentation

* document change in changelog

CHANGELOG.rst

@@ -31,6 +31,7 @@ Interactive improvements
 - Escape during history search restores the original commandline again (regressed in 3.6.0).
 - Using ``--help`` on builtins now respects the $MANPAGER variable in preference to $PAGER (:issue:`9488`).
 - Command-specific tab completions may now offer results whose first character is a period. For example, it is now possible to tab-complete ``git add`` for files with leading periods. The default file completions hide these files, unless the token itself has a leading period (:issue:`3707`).
+- A new variable, :envvar:`fish_cursor_external`, can be used to specify to cursor shape when a command is launched. When unspecified, the value defaults to the value of :envvar:`fish_cursor_default` (:issue:`4656`).
 
 New or improved bindings
 ^^^^^^^^^^^^^^^^^^^^^^^^

doc_src/interactive.rst

@@ -420,6 +420,9 @@ The ``fish_vi_cursor`` function will be used to change the cursor's shape depend
    set fish_cursor_insert line
    # Set the replace mode cursor to an underscore
    set fish_cursor_replace_one underscore
+   # Set the external cursor to a line. The external cursor appears when a command is started. 
+   # The cursor shape takes the value of fish_cursor_default when fish_cursor_external is not specified.
+   set fish_cursor_external line
    # The following variable can be used to configure cursor shape in
    # visual mode, but due to fish_cursor_default, is redundant here
    set fish_cursor_visual block

share/functions/fish_vi_cursor.fish

@@ -92,7 +92,10 @@ function fish_vi_cursor -d 'Set cursor shape for different vi modes'
 
     echo "
           function fish_vi_cursor_handle_preexec --on-event fish_preexec
-              set -l varname fish_cursor_default
+              set -l varname fish_cursor_external
+              if not set -q \$varname
+                set varname fish_cursor_default
+              end
               if not set -q \$varname
                 set varname fish_cursor_unknown
               end