koji: only pull --rebase if remote is initialized

After running 'make autospecnew', the freshly created repo only exists locally,
so the repo remote is not yet initialized. The 'git pull --rebase' (via 'make
koji') will then fail due to the uninitialized remote. Improve this case by
only rebasing when the remote is initialized.

Signed-off-by: Patrick McCarty <patrick.mccarty@intel.com>

Makefile.common

@@ -286,8 +286,10 @@ koji: prekoji-checks kojidef
 	@if ! git branch | grep -q -E '^\* master'; then \
 		echo "Error: Must be on the master branch to submit to koji" >&2; \
 		exit 1; \
+	fi; \
+	if git rev-parse --verify --quiet origin/master > /dev/null; then \
+		git pull --rebase; \
 	fi
-	git pull --rebase
 	git tag $(SRPMVERS)
 	git push origin master refs/tags/$(SRPMVERS)
 	$(KOJI_CMD) build $$KOJI_NOWAIT $(KOJI_TAG) $(PKG_BASE_URL)/$(PKG_NAME)?#$(SRPMVERS)