rebase: print "Nothing changed" when source set is empty #547

Job	Run time
Build binary artifacts (linux-x86_64-musl)	36s
Build binary artifacts (linux-x86_64-musl)	35s
Build binary artifacts (linux-x86_64-musl)	35s
Build binary artifacts (linux-x86_64-gnu)	5m 55s
Build binary artifacts (linux-x86_64-gnu)	5m 55s
Build binary artifacts (linux-x86_64-gnu)	5m 55s
Build binary artifacts (linux-aarch64-musl)	6m 18s
Build binary artifacts (linux-aarch64-musl)	6m 18s
Build binary artifacts (linux-aarch64-musl)	6m 18s
Build binary artifacts (linux-aarch64-gnu)	6m 0s
Build binary artifacts (linux-aarch64-gnu)	6m 0s
Build binary artifacts (linux-aarch64-gnu)	6m 0s
Build binary artifacts (macos-x86_64)	11m 26s
Build binary artifacts (macos-x86_64)	11m 26s
Build binary artifacts (macos-x86_64)	11m 26s
Build binary artifacts (macos-aarch64)	4m 29s
Build binary artifacts (macos-aarch64)	4m 29s
Build binary artifacts (macos-aarch64)	4m 29s
Build binary artifacts (win-x86_64)	9m 39s
Build binary artifacts (win-x86_64)	9m 39s
Build binary artifacts (win-x86_64)	9m 39s
	2h 13m 7s

Provide feedback