Resolves #17

README.markdown

@@ -31,7 +31,7 @@ This plugin gives syntax highlighting to [todo.txt](http://todotxt.com/) files.
 
 `<leader>-X` : Mark all tasks as completed
 
-`<leader>-D` : Remove completed tasks
+`<leader>-D` : Move completed tasks to done.txt
 
 If you want the help installed, run ":helptags ~/.vim/doc" inside vim after having copied the files.
 Then you will be able to get the commands help with: :h todo.txt

doc/todo.txt

@@ -27,6 +27,6 @@ COMMANDS                                                       *todo-commands*
 
 `<leader>-X` : Mark all tasks as completed
 
-`<leader>-D` : Remove completed tasks
+`<leader>-D` : Move completed tasks to done.txt
 
 <leader> is \ by default, so <leader>-s means you type \s

done.txt

@@ -1,4 +1,3 @@
-2014-11-01 Find a way to import text into markdown and vim doc @doc
 x 2011-05-30 Create README.markdown to be published in github @doc
 x 2011-05-30 Implement colorized priorities @syntax
 x 2011-05-30 Implement filetype detection @ftdetect

ftplugin/todo.vim

@@ -35,8 +35,33 @@ function! TodoTxtMarkAllAsDone()
 function! TodoTxtMarkAllAsDone()
     :g!/^x /:call TodoTxtMarkAsDone()
 endfunction
+
+function! s:AppendToFile(file, lines)
+    let l:lines = []
+
+    " Place existing tasks in done.txt at the beggining of the list.
+    if filereadable(a:file)
+        call extend(l:lines, readfile(a:file))
+    endif
+
+    " Append new completed tasks to the list.
+    call extend(l:lines, a:lines)
+
+    " Write to file.
+    call writefile(l:lines, a:file)
+endfunction
 
-function! TodoTxtRemoveCompleted()
+function! TodoTxtRemoveCompleted()
+    " Check if we can write to done.txt before proceeding.
+    let l:target_dir = expand('%:p:h')
+    let l:done_file = l:target_dir.'/done.txt'
+    if !filewritable(l:done_file) && !filewritable(l:target_dir)
+        echoerr "Can't write to file 'done.txt'"
+        return
+    endif
+
+    let l:completed = []
+    :g/^x /call add(l:completed, getline(line(".")))|d
     call s:AppendToFile(l:done_file, l:completed)
 endfunction
 

todo.txt

@@ -0,0 +1 @@
+2014-11-01 Find a way to import text into markdown and vim doc @doc