Pass cursor position to edit_command_buffer for some editors

Fixes #6138

Naturally this does not work for many other editors/aliases,
but it's still nice that we can make it work for some common
editors without requiring any configuration.

Of course this approach is not terribly flexible; but it's
alwyas possible to just wrap edit_command_buffer and set an
EDITOR that knows about the cursor position. It doesn't
feel important enough to add a configuration option.

share/functions/edit_command_buffer.fish

@@ -29,8 +29,34 @@ function edit_command_buffer --description 'Edit the command buffer in an extern
     end
 
     commandline -b >$f
+    set -l offset (commandline --cursor)
+    # compute cursor line/column
+    set -l lines (commandline)\n
+    set -l line 1
+    while test $offset -ge (string length $lines[1])
+        set offset (math $offset - (string length $lines[1]))
+        set line (math $line + 1)
+        set -e lines[1]
+    end
+    set col (math $offset + 1)
+
+    set -l basename (string match -r '[^/]*$' -- $editor[1])
+    if contains $basename vi vim nvim
+        set -a editor +$line +"norm $col|" $f
+    else if contains $basename emacs emacsclient gedit kak
+        set -a editor +$line:$col $f
+    else if contains $basename nano
+        set -a editor +$line,$col $f
+    else if contains $basename joe ee
+        set -a editor +$line $f
+    else if contains $basename code code-oss
+        set -a editor --goto $f:$line:$col
+    else
+        set -a editor $f
+    end
+
     __fish_disable_bracketed_paste
-    $editor $f
+    $editor
     set -l editor_status $status
     __fish_enable_bracketed_paste