Don't git fetch if sha revision is up-to-date

If you're using a sha as your revision parameter and the current HEAD is
already pointing at that sha, there's no need to do a git fetch.

Making this change should significantly reduce the number of calls made
to the remote Git server; since the catalog hasn't changed, you'll be
up-to-date and not do the fetch call.

Author: vpierson

lib/puppet/provider/vcsrepo/git.rb

@@ -503,6 +503,11 @@ def latest_revision
   # @return [String] Returns the tag/branch of the current repo if it's up to
   #                  date; otherwise returns the sha of the requested revision.
   def get_revision(rev = 'HEAD')
+    current = at_path { git_with_identity('rev-parse', rev).strip }
+    if @resource.value(:revision) == current
+      # if already pointed at desired revision, it must be a SHA, so just return it
+      return current
+    end
     if @resource.value(:source)
       update_references
     else
@@ -514,7 +519,6 @@ def get_revision(rev = 'HEAD')
         return branch
       end
     end
-    current = at_path { git_with_identity('rev-parse', rev).strip }
     if @resource.value(:revision)
       canonical = if tag_revision?
                     # git-rev-parse will give you the hash of the tag object itself rather

spec/unit/puppet/provider/vcsrepo/git_spec.rb

@@ -298,8 +298,8 @@ def branch_a_list(include_branch = nil?)
       it 'returns the current SHA' do
         resource[:revision] = 'currentsha'
         provider.stubs(:git).with('branch', '-a').returns(branch_a_list)
-        provider.expects(:git).with('rev-parse', '--revs-only', resource.value(:revision)).returns('currentsha')
-        provider.expects(:update_references)
+        provider.expects(:git).with('rev-parse', '--revs-only', resource.value(:revision)).never
+        provider.expects(:update_references).never
         expect(provider.revision).to eq(resource.value(:revision))
       end
     end