Don't use -u in git diff-tree

Review Request #8222 — Created June 7, 2016 and submitted — Latest diff uploaded

Information

RBTools
release-0.7.x
e103333...

Reviewers

When generating diffs for SVN and Perforce with excluded files, we would
pass -u to git diff-tree, which generates diff output instead of the
list of changed files and break the parsing. Now, we remove the -u
flag from the git diff-tree command when generating the excluded files
list for SVN or Perforce repositories.