Add command to create a directory in a new category "files"

Use the alt + (left click) is tree view to create a directory and
shift + (middle click) to remove a project directory.

data/core/command.lua

@@ -59,7 +59,7 @@ end
 
 
 function command.add_defaults()
-  local reg = { "core", "root", "command", "doc", "findreplace" }
+  local reg = { "core", "root", "command", "doc", "findreplace", "files" }
   for _, name in ipairs(reg) do
     require("core.commands." .. name)
   end

data/core/commands/files.lua

@@ -0,0 +1,13 @@
+local core = require "core"
+local command = require "core.command"
+
+command.add(nil, {
+  ["files:create-directory"] = function()
+    core.command_view:enter("New directory name", function(text)
+      local success, err = system.mkdir(text)
+      if not success then
+        core.error("cannot create directory %q: %s", text, err)
+      end
+    end)
+  end,
+})

data/plugins/treeview.lua

@@ -137,12 +137,29 @@ function TreeView:on_mouse_moved(px, py)
 end
 
 
+local function create_directory_in(item)
+  local path = item.abs_filename
+  local basename = path:match("[^\\/]+$")
+  core.command_view:enter("Create directory in " .. basename, function(text)
+    local dirname = path .. PATHSEP .. text
+    local success, err = system.mkdir(dirname)
+    if not success then
+      core.error("cannot create directory %q: %s", dirname, err)
+    end
+    item.expanded = true
+    core.request_project_scan()
+  end)
+end
+
+
 function TreeView:on_mouse_pressed(button, x, y)
   if not self.hovered_item then
     return
   elseif self.hovered_item.type == "dir" then
-    if button == "middle" and self.hovered_item.depth == 0 then
+    if keymap.modkeys["shift"] and button == "middle" and self.hovered_item.depth == 0 then
       core.remove_project_directory(self.hovered_item.abs_filename)
+    elseif keymap.modkeys["alt"] and button == "left" then
+      create_directory_in(self.hovered_item)
     else
       self.hovered_item.expanded = not self.hovered_item.expanded
     end