test-rebuild.sh: check branch agrees with installation

tests/test-rebuild.sh

@@ -21,10 +21,19 @@ ARCH=$(arch)
 #  exit 1
 #fi
 
+eval $(grep VERSION_ID /etc/os-release)
+BRANCH="f$VERSION_ID"
+
+# maybe use BRANCH here too?
 if [ -n "$2" ]; then
   fedpkg switch-branch $2
 fi
 
+if [ "* $BRANCH" != "$(git branch --list $BRANCH" ]; then
+  echo "Git branch does not match Fedora installation!"
+  exit 1
+fi
+
 sudo yum-builddep $PKG.spec
 
 fedpkg local