--- a/runtime/macros/README.txt
+++ b/runtime/macros/README.txt
@@ -12,11 +12,19 @@ The other files contain some handy utili
 how to use Vi and Vim functionality.
 
 dvorak			for when you use a Dvorak keyboard
+
 justify.vim		user function for justifying text
+
 matchit.vim + matchit.txt  make % match if-fi, HTML tags, and much more
+
 less.sh + less.vim	make Vim work like less (or more)
+
 shellmenu.vim		menus for editing shell scripts in the GUI version
+
 swapmous.vim		swap left and right mouse buttons
 
+editexisting.vim	when editing a file that is already edited with
+			another Vim instance
+
 This one is only for Unix.  It can be found in the extra archive:
 file_select.vim		macros that make a handy file selector

new file mode 100644
--- /dev/null
+++ b/runtime/macros/editexisting.vim
@@ -0,0 +1,97 @@
+" Vim Plugin: 	Edit the file with an existing Vim if possible
+" Maintainer:	Bram Moolenaar
+" Last Change:	2005 Dec 11
+
+" This is a plugin, drop it in your (Unix) ~/.vim/plugin or (Win32)
+" $VIM/vimfiles/plugin directory.
+
+" This plugin serves two purposes:
+" 1. On startup, if we were invoked with one file name argument and the file
+"    is not modified then try to find another Vim instance that is editing
+"    this file.  If there is one then bring it to the foreground and exit.
+" 2. When a file is edited and a swap file exists for it, try finding that
+"    other Vim and bring it to the foreground.  Requires Vim 7, because it
+"    uses the SwapExists autocommand event.
+
+" Function that finds the Vim instance that is editing "filename" and brings
+" it to the foreground.
+func s:EditElsewhere(filename)
+  let fname_esc = substitute(a:filename, "'", "''", "g")
+
+  let servers = serverlist()
+  while servers != ''
+    " Get next server name in "servername"; remove it from "servers".
+    let i = match(servers, "\n")
+    if i == -1
+      let servername = servers
+      let servers = ''
+    else
+      let servername = strpart(servers, 0, i)
+      let servers = strpart(servers, i + 1)
+    endif
+
+    " Skip ourselves.
+    if servername ==? v:servername
+      continue
+    endif
+   
+    " Check if this server is editing our file.
+    if remote_expr(servername, "bufloaded('" . fname_esc . "')")
+      " Yes, bring it to the foreground.
+      if has("win32")
+	call remote_foreground(servername)
+      endif
+      call remote_expr(servername, "foreground()")
+
+      " Make sure the file is visible in a window (not hidden).
+      " If v:swapcommand exists and is set, send it to the server.
+      if exists("v:swapcommand")
+	let c = substitute(v:swapcommand, "'", "''", "g")
+	call remote_expr(servername, "EditExisting('" . fname_esc . "', '" . c . "')")
+      else
+	call remote_expr(servername, "EditExisting('" . fname_esc . "', '')")
+      endif
+
+      if !(has('vim_starting') && has('gui_running') && has('gui_win32'))
+	" Tell the user what is happening.  Not when the GUI is starting
+	" though, it would result in a message box.
+	echomsg "File is being edited by " . servername
+	sleep 2
+      endif
+      return 'q'
+    endif
+  endwhile
+  return ''
+endfunc
+
+" When the plugin is loaded and there is one file name argument: Find another
+" Vim server that is editing this file right now.
+if argc() == 1 && !&modified
+  if s:EditElsewhere(expand("%:p")) == 'q'
+    quit
+  endif
+endif
+
+" Setup for handling the situation that an existing swap file is found.
+try
+  au! SwapExists * let v:swapchoice = s:EditElsewhere(expand("<afile>:p"))
+catch
+  " Without SwapExists we don't do anything for ":edit" commands
+endtry
+
+" Function used on the server to make the file visible and possibly execute a
+" command.
+func! EditExisting(fname, command)
+  let n = bufwinnr(a:fname)
+  if n > 0
+    exe n . "wincmd w"
+  else
+    exe "split " . escape(a:fname, ' #%"|')
+  endif
+
+  if a:command != ''
+    exe "normal " . a:command
+  endif
+
+  redraw
+endfunc

--- a/src/fileio.c
+++ b/src/fileio.c
@@ -2534,15 +2534,16 @@ set_file_time(fname, atime, mtime)
 #endif
 
 /*
- * buf_write() - write to file 'fname' lines 'start' through 'end'
+ * buf_write() - write to file "fname" lines "start" through "end"
  *
  * We do our own buffering here because fwrite() is so slow.
  *
- * If forceit is true, we don't care for errors when attempting backups (jw).
- * In case of an error everything possible is done to restore the original file.
- * But when forceit is TRUE, we risk loosing it.
- * When reset_changed is TRUE and start == 1 and end ==
- * curbuf->b_ml.ml_line_count, reset curbuf->b_changed.
+ * If "forceit" is true, we don't care for errors when attempting backups.
+ * In case of an error everything possible is done to restore the original
+ * file.  But when "forceit" is TRUE, we risk loosing it.
+ *
+ * When "reset_changed" is TRUE and "append" == FALSE and "start" == 1 and
+ * "end" == curbuf->b_ml.ml_line_count, reset curbuf->b_changed.
  *
  * This function must NOT use NameBuff (because it's called by autowrite()).
  *
@@ -2557,7 +2558,7 @@ buf_write(buf, fname, sfname, start, end
     linenr_T	    start, end;
     exarg_T	    *eap;		/* for forced 'ff' and 'fenc', can be
 					   NULL! */
-    int		    append;
+    int		    append;		/* append to the file */
     int		    forceit;
     int		    reset_changed;
     int		    filtering;
@@ -2652,7 +2653,8 @@ buf_write(buf, fname, sfname, start, end
      * If there is no file name yet, use the one for the written file.
      * BF_NOTEDITED is set to reflect this (in case the write fails).
      * Don't do this when the write is for a filter command.
-     * Only do this when 'cpoptions' contains the 'f' flag.
+     * Don't do this when appending.
+     * Only do this when 'cpoptions' contains the 'F' flag.
      */
     if (reset_changed
 	    && whole
@@ -2662,6 +2664,7 @@ buf_write(buf, fname, sfname, start, end
 #endif
 	    && buf->b_ffname == NULL
 	    && !filtering
+	    && (!append || vim_strchr(p_cpo, CPO_FNAMEAPP) != NULL)
 	    && vim_strchr(p_cpo, CPO_FNAMEW) != NULL)
     {
 #ifdef FEAT_AUTOCMD
@@ -2826,9 +2829,12 @@ buf_write(buf, fname, sfname, start, end
 		{
 		    /* Assume the buffer was written, update the timestamp. */
 		    ml_timestamp(buf);
-		    buf->b_flags &= ~BF_WRITE_MASK;
+		    if (append)
+			buf->b_flags &= ~BF_NEW;
+		    else
+			buf->b_flags &= ~BF_WRITE_MASK;
 		}
-		if (reset_changed && buf->b_changed
+		if (reset_changed && buf->b_changed && !append
 			&& (overwriting || vim_strchr(p_cpo, CPO_PLUS) != NULL))
 		    /* Buffer still changed, the autocommands didn't work
 		     * properly. */
@@ -4232,7 +4238,7 @@ restore_backup:
 
     /* When written everything correctly: reset 'modified'.  Unless not
      * writing to the original file and '+' is not in 'cpoptions'. */
-    if (reset_changed && whole
+    if (reset_changed && whole && !append
 #ifdef FEAT_MBYTE
 	    && !write_info.bw_conv_error
 #endif
@@ -4250,7 +4256,10 @@ restore_backup:
     if (overwriting)
     {
 	ml_timestamp(buf);
-	buf->b_flags &= ~BF_WRITE_MASK;
+	if (append)
+	    buf->b_flags &= ~BF_NEW;
+	else
+	    buf->b_flags &= ~BF_WRITE_MASK;
     }
 
     /*

--- a/src/tag.c
+++ b/src/tag.c
@@ -843,11 +843,22 @@ do_tag(tag, type, count, forceit, verbos
 		}
 	    }
 
+#ifdef FEAT_AUTOCMD
+	    /* Let the SwapExists event know what tag we are jumping to. */
+	    vim_snprintf((char *)IObuff, IOSIZE, ":ta %s\r", name);
+	    set_vim_var_string(VV_SWAPCOMMAND, IObuff, -1);
+#endif
+
 	    /*
 	     * Jump to the desired match.
 	     */
-	    if (jumpto_tag(matches[cur_match], forceit, type != DT_CSCOPE)
-								 == NOTAGFILE)
+	    i = jumpto_tag(matches[cur_match], forceit, type != DT_CSCOPE);
+
+#ifdef FEAT_AUTOCMD
+	    set_vim_var_string(VV_SWAPCOMMAND, NULL, -1);
+#endif
+
+	    if (i == NOTAGFILE)
 	    {
 		/* File not found: try again with another matching tag */
 		if ((type == DT_PREV && cur_match > 0)