Add option to expand VimuxPromptCommand arguments (#166)

Co-authored-by: Gerhard Siegesmund <gerhard.siegesmund@btd.de>

doc/vimux.txt

@@ -400,5 +400,21 @@ you're using panes or windows, and your version of tmux.
 
 Default: "tmux"
 
+------------------------------------------------------------------------------
+                                                            VimuxExpandCommand
+4.10 g:VimuxExpandCommand~
+
+Should the command given at the prompt via VimuxPromptCommand be expanded
+using expand(). 1 to expand the string.
+
+Unfortunately expand() only expands % (etc.) if the string starts with that
+character. So the command is split at spaces and then rejoined after
+expansion. With this simple approach things like "%:h/test.xml" are not
+possible.
+
+  let g:VimuxExpandCommand = 1
+
+Default: 0
+
 ==============================================================================
 vim:tw=78:ts=2:sw=2:expandtab:ft=help:norl:

plugin/vimux.vim

@@ -14,6 +14,7 @@ let g:VimuxRunnerName    = get(g:, 'VimuxRunnerName',    '')
 let g:VimuxRunnerType    = get(g:, 'VimuxRunnerType',    'pane')
 let g:VimuxTmuxCommand   = get(g:, 'VimuxTmuxCommand',   'tmux')
 let g:VimuxUseNearest    = get(g:, 'VimuxUseNearest',    v:true)
+let g:VimuxExpandCommand = get(g:, 'VimuxExpandCommand', v:false)
 
 function! VimuxOption(name) abort
   return get(b:, a:name, get(g:, a:name))
@@ -167,6 +168,9 @@ endfunction
 function! VimuxPromptCommand(...)
   let command = a:0 ==# 1 ? a:1 : ''
   let l:command = input(VimuxOption('VimuxPromptString'), command, 'shellcmd')
+  if VimuxOption('VimuxExpandCommand')
+    let l:command = join(map(split(l:command, ' '), 'expand(v:val)'), ' ')
+  endif
   call VimuxRunCommand(l:command)
 endfunction