Create Changelog when performing BundleInstall!

Keeps track of the current commit with a vundle_update tag before
perfoming an update and adds all commits pulled in the update to a
Changelog accessible via pressing 'u' after BundleInstall! completes.

autoload/vundle/scripts.vim

@@ -33,6 +33,33 @@ func! s:view_log()
   wincmd P | wincmd H
 endf
 
+func! s:create_changelog() abort
+  for bundle in g:updated_bundles
+    let updates = system('cd '.shellescape(bundle.path()).
+          \              ' && git log --pretty=format:"%s   %an, %ar" --graph'.
+          \              ' vundle_update..HEAD')
+    call add(g:vundle_changelog, '')
+    call add(g:vundle_changelog, 'Updated Bundle: '.bundle.name)
+    for update in split(updates, '\n')
+      let update = substitute(update, '\s\+$', '', '')
+      call add(g:vundle_changelog, '  '.update)
+    endfor
+  endfor
+endf
+
+func! s:view_changelog()
+  call s:create_changelog()
+
+  if !exists('g:vundle_changelog_file')
+    let g:vundle_changelog_file = tempname()
+  endif
+
+  call writefile(g:vundle_changelog, g:vundle_changelog_file)
+  silent pedit `=g:vundle_changelog_file`
+
+  wincmd P | wincmd H
+endf
+
 func! vundle#scripts#bundle_names(names)
   return map(copy(a:names), ' printf("Bundle ' ."'%s'".'", v:val) ')
 endf
@@ -80,6 +107,7 @@ func! vundle#scripts#view(title, headers, results)
 
   com! -buffer -nargs=0 VundleLog call s:view_log()
 
+  com! -buffer -nargs=0 VundleChangelog call s:view_changelog()
 
   nnoremap <buffer> q :silent bd!<CR>
   nnoremap <buffer> D :exec 'Delete'.getline('.')<CR>
@@ -91,6 +119,7 @@ func! vundle#scripts#view(title, headers, results)
   nnoremap <buffer> I :exec 'InstallAndRequire'.substitute(getline('.'), '^Bundle ', 'Bundle! ', '')<CR>
 
   nnoremap <buffer> l :VundleLog<CR>
+  nnoremap <buffer> u :VundleChangelog<CR>
   nnoremap <buffer> h :h vundle<CR>
   nnoremap <buffer> ? :norm h<CR>