add option to make width a percentage of "&columns" (#473)

Author: booperlv

README.md

@@ -18,7 +18,7 @@ Plug 'kyazdani42/nvim-tree.lua'
 
 ```vim
 let g:nvim_tree_side = 'right' "left by default
-let g:nvim_tree_width = 40 "30 by default
+let g:nvim_tree_width = 40 "30 by default, can be width_in_columns or 'width_in_percent%'
 let g:nvim_tree_ignore = [ '.git', 'node_modules', '.cache' ] "empty by default
 let g:nvim_tree_gitignore = 1 "0 by default
 let g:nvim_tree_auto_open = 1 "0 by default, opens the tree when typing `vim $DIR` or `vim`

doc/nvim-tree-lua.txt

@@ -54,7 +54,10 @@ OPTIONS				                  *nvim-tree-options*
 
 |g:nvim_tree_width|				*g:nvim_tree_width*
 
-width of the window (default to 30)
+width of the window, can be *width_in_columns* or *'width_in_percent%'*
+>
+    let g:nvim_tree_width = 30 " indicates width of 30 columns
+    let g:nvim_tree_width = '30%' " indicates width of 30% of '&columns'
 
 |g:nvim_tree_side|				*g:nvim_tree_side*
 

lua/nvim-tree/view.lua

@@ -214,12 +214,21 @@ function M.focus(winnr, open_if_closed)
   a.nvim_set_current_win(wnr)
 end
 
+local function get_width()
+  if type(M.View.width) == "number" then
+    return M.View.width
+  end
+  local width_as_number = tonumber(M.View.width:sub(0, -2))
+  local percent_as_decimal = width_as_number / 100
+  return math.floor(vim.o.columns * percent_as_decimal)
+end
+
 function M.resize()
   if vim.g.nvim_tree_auto_resize == 0 or not a.nvim_win_is_valid(M.get_winnr()) then
     return
   end
 
-  a.nvim_win_set_width(M.get_winnr(), M.View.width)
+  a.nvim_win_set_width(M.get_winnr(), get_width())
 end
 
 local move_tbl = {
@@ -237,7 +246,7 @@ function M.open()
   a.nvim_command("vsp")
   local move_to = move_tbl[M.View.side]
   a.nvim_command("wincmd "..move_to)
-  a.nvim_command("vertical resize "..M.View.width)
+  a.nvim_command("vertical resize "..get_width())
   local winnr = a.nvim_get_current_win()
   local tabpage = a.nvim_get_current_tabpage()
   M.View.tabpages[tabpage] = vim.tbl_extend("force", M.View.tabpages[tabpage] or {help = false}, {winnr = winnr})