Add line deletion to StripTrailingWhitespace()

In addition to its existing functionality of removing trailing spaces
from the ends of lines, this change has the function remove lines at the
end of the file afterwards if they contain no non-whitespace characters,
based on its observations during the line iteration.

This uses the older VimL functions line() and col() in preference to the
newer winsaveview() and winrestview() to restore the cursor position
after the range :delete moves it, so that this will hopefully work even
on older versions of Vim; that is not yet tested.

I am surprised that there is no line deletion function to match e.g.
getline(), setline(), but it does seem to be the case:
<https://groups.google.com/d/msg/vim_use/TY9NmJXh8EU/iFjOUg68AekJ>

1 files changed, 26 insertions, 0 deletions

diff --git a/vim/config/whitespace.vim b/vim/config/whitespace.vim
index d44ba333..d678ae8a 100644
--- a/vim/config/whitespace.vim
+++ b/vim/config/whitespace.vim
@@ -11,6 +11,9 @@ if has('eval')
     " Iterating line number
     let l:li = 1
 
+    " Line number of last line that had non-whitespace characters on it
+    let l:lw = 0
+
     " Line number of the file's last line
     let l:ll = line('$')
 
@@ -24,9 +27,32 @@ if has('eval')
       " whitespace
       call setline(l:li, substitute(l:line, '\m\C\s\+$', '', 'g'))
 
+      " If this line has any non-whitespace characters on it, update l:lw with
+      " its index
+      if l:line =~# '\m\C\S'
+        let l:lw = l:li
+      endif
+
       " Increment the line counter for the next iteration
       let l:li = l:li + 1
     endwhile
+
+    " If the last non-whitespace line was before the last line proper, we can
+    " delete all lines after it
+    if l:lw < l:ll
+
+      " Get the current line and column so we can return to it
+      " (Yes I know about winsaveview() and winrestview(); I want this to work
+      " even on very old versions of Vim if possible)
+      let l:lc = line('.')
+      let l:cc = col('.')
+
+      " Delete the lines, which will move the cursor
+      execute l:lw + 1.',$ delete'
+
+      " Return the cursor to the saved position
+      call cursor(l:lc, l:cc)
+    endif
   endfunction
 
   " Map \x to the function just defined