Don't rely on `git` command output.

This commit introduces `rev-parse HEAD` in order to parse the commits at
which HEAD points before and after `git pull`. If the commits are the
same, the bundle is considered 'up-to-date'. If the commits are different,
then the HEAD was fast-forwarded and the bundle is considered 'updated'.

This approach is more reliable than parsing the output of the `git` command
as it can differ between OSes and locales.

Tested on Ubuntu 11.10. The control characters at the end of the output of
`git rev-parse` are stripped away using '[:cntrl:]', assuming cross-platform.

autoload/vundle/installer.vim

@@ -201,50 +201,65 @@ func! s:helptags(rtp) abort
 endf
 
 func! s:sync(bang, bundle) abort
+  call s:log('')
+  call s:log('Bundle '.a:bundle.name_spec)
+
   let git_dir = expand(a:bundle.path().'/.git/', 1)
   if isdirectory(git_dir)
     if !(a:bang) | return 'todate' | endif
-    let cmd = 'cd '.shellescape(a:bundle.path()).' && git pull'
+    let change_cmd = 'cd '.shellescape(a:bundle.path())
 
     if (has('win32') || has('win64'))
-      let cmd = substitute(cmd, '^cd ','cd /d ','')  " add /d switch to change drives
-      let cmd = '"'.cmd.'"'                          " enclose in quotes
+      let change_cmd = substitute(change_cmd, '^cd ','cd /d ','')  " add /d switch to change drives
+      let change_cmd = '"'.change_cmd.'"'                          " enclose in quotes
+  endif
+
+    let cmd = change_cmd.' && git rev-parse HEAD'
+    let initial_sha = s:system(cmd)
+
+    if 0 != v:shell_error | return 'error' | endif
+
+    let cmd = change_cmd.' && git pull'
+    let out = s:system(cmd)
+    call s:log('$ '.cmd)
+    call s:log('> '.out)
+
+    if 0 != v:shell_error | return 'error' | endif
+
+    let cmd = change_cmd.' && git rev-parse HEAD'
+    let updated_sha = s:system(cmd)
+
+    if 0 != v:shell_error | return 'error' | endif
+
+    let initial_sha = s:strip_right(initial_sha)
+    let updated_sha = s:strip_right(updated_sha)
+
+    if initial_sha == updated_sha
+      return 'todate'
     endif
+
+    call add(g:updated_bundles, [initial_sha, updated_sha, a:bundle])
+    return 'updated'
   else
     let cmd = 'git clone '.a:bundle.uri.' '.shellescape(a:bundle.path())
-  endif
 
-  let out = s:system(cmd)
-  call s:log('')
-  call s:log('Bundle '.a:bundle.name_spec)
-  call s:log('$ '.cmd)
-  call s:log('> '.out)
+    let out = s:system(cmd)
+    call s:log('$ '.cmd)
+    call s:log('> '.out)
 
-  if 0 != v:shell_error
-    return 'error'
-  end
+    if 0 != v:shell_error | return 'error' | endif
 
-  if out =~# 'Cloning into '
     return 'new'
-  elseif out =~# 'up-to-date'
-    return 'todate'
   endif
-
-  call s:add_to_updated_bundles(out, a:bundle)
-  return 'updated'
 endf
 
 func! s:system(cmd) abort
   return system(a:cmd)
 endf
 
-func! s:add_to_updated_bundles(out, bundle) abort
-  let git_pull_shas = matchlist(a:out, 'Updating \(\w\+\)..\(\w\+\)')
-  let initial_sha = git_pull_shas[1]
-  let updated_sha = git_pull_shas[2]
-
-  call add(g:updated_bundles, [initial_sha, updated_sha, a:bundle])
-endfunc
+func! s:strip_right(input)
+  return substitute(a:input, '[[:space:][:cntrl:]]\+$', '', '')
+endfunction
 
 func! s:log(str) abort
   let fmt = '%y%m%d %H:%M:%S'