Version 2.9

 � Avoid tag updating when ctags output has identical fingerprint (contributed by Ingo Karkat):   http://github.com/xolox/vim-easytags/commit/d789e8e   http://github.com/xolox/vim-easytags/commit/92d1f2d   http://github.com/xolox/vim-easytags/commit/07437cf

.gitignore

@@ -0,0 +1 @@
+doc/tags

autoload/xolox/easytags.vim

@@ -1,9 +1,9 @@
 " Vim script
 " Author: Peter Odding <peter@peterodding.com>
-" Last Change: April 18, 2013
+" Last Change: April 19, 2013
 " URL: http://peterodding.com/code/vim/easytags/
 
-let g:xolox#easytags#version = '2.8.2'
+let g:xolox#easytags#version = '2.9'
 
 " Public interface through (automatic) commands. {{{1
 
@@ -99,8 +99,11 @@ function! xolox#easytags#update(silent, filter_tags, filenames) " {{{2
     let tagsfile = xolox#easytags#get_tagsfile()
     let firstrun = !filereadable(tagsfile)
     let cmdline = s:prep_cmdline(cfile, tagsfile, firstrun, a:filenames, context)
-    let output = s:run_ctags(starttime, cfile, tagsfile, firstrun, cmdline)
+    let [output, has_updates] = s:run_ctags(starttime, cfile, tagsfile, firstrun, cmdline)
     if !firstrun
+      if !has_updates
+        return 1
+      endif
       if have_args && !empty(g:easytags_by_filetype)
         " TODO Get the headers from somewhere?!
         call s:save_by_filetype(a:filter_tags, [], output, context)
@@ -203,10 +206,12 @@ endfunction
 
 function! s:run_ctags(starttime, cfile, tagsfile, firstrun, cmdline) " {{{3
   let lines = []
+  let has_updates = 1
   if a:cmdline != ''
     call xolox#misc#msg#debug("easytags.vim %s: Executing %s.", g:xolox#easytags#version, a:cmdline)
     try
       let lines = xolox#shell#execute(a:cmdline, 1)
+      let has_updates = a:firstrun || s:has_updates(a:cfile, join(lines, "\n"))
     catch /^Vim\%((\a\+)\)\=:E117/
       " Ignore missing shell.vim plug-in.
       let output = system(a:cmdline)
@@ -215,6 +220,7 @@ function! s:run_ctags(starttime, cfile, tagsfile, firstrun, cmdline) " {{{3
         throw printf(msg, fnamemodify(a:tagsfile, ':~'), strtrans(output))
       endif
       let lines = split(output, "\n")
+      let has_updates = a:firstrun || s:has_updates(a:cfile, output)
     endtry
     if a:firstrun
       if a:cfile != ''
@@ -225,9 +231,47 @@ function! s:run_ctags(starttime, cfile, tagsfile, firstrun, cmdline) " {{{3
       return []
     endif
   endif
-  return xolox#easytags#parse_entries(lines)
+  return [xolox#easytags#parse_entries(lines), has_updates]
 endfunction
 
+" Vim 7.3 now has the sha256() function. We use it below to recognize when the
+" tags haven't changed from the last time we ran Exuberant Ctags on a file; in
+" this case the tags file doesn't have to be written to disk which makes the
+" plug-in much faster for a very common case.
+
+let s:fingerprints = {}
+
+function! s:has_updates(cfile, output)
+  if empty(a:cfile)
+    " The cache doesn't work when tags aren't created for the current file.
+    return 1
+  endif
+  let fingerprint = s:get_fingerprint(a:cfile, a:output)
+  call xolox#misc#msg#debug("easytags.vim %s: Fingerprint of tags in %s is %s.", g:xolox#easytags#version, a:cfile, string(fingerprint))
+  if !empty(fingerprint) && get(s:fingerprints, a:cfile, '') ==# fingerprint
+    call xolox#misc#msg#debug("easytags.vim %s: The fingerprint didn't change! We can take a shortcut :-)", g:xolox#easytags#version)
+    return 0
+  endif
+  let s:fingerprints[a:cfile] = fingerprint
+  return 1
+endfunction
+
+if exists('*sha256')
+  function! s:get_fingerprint(cfile, output)
+    return sha256(a:output)
+  endfunction
+else
+  function! s:get_fingerprint(cfile, output)
+    " Don't want to re-implement a costly hashing function in Vimscript. Just
+    " handle files that never had any tags.
+    if empty(a:output)
+      return get(s:fingerprints, a:cfile, 1)
+    else
+      return ''
+    endif
+  endfunction
+endif
+
 function! s:filter_merge_tags(filter_tags, tagsfile, output, context) " {{{3
   let [headers, entries] = xolox#easytags#read_tagsfile(a:tagsfile)
   let filters = []