SCM - the refresh action does not refresh the history graph

[lszomoru]

Steps to Reproduce:

1. Open a folder/workspace that contains a git repository
2. Create some commits so that you have some outgoing changes in the history graph
3. Open the output window, switch to the Git output channel, and clear the contents
4. Click the "Refresh" action in the "Source Control" viewlet
5. You should see a git log entry int the output channel