[HfApi] prevent empty commits when copying files #6992

Job	Run time
build-windows (3.8)	4m 41s
build-ubuntu (3.8, Repository only)	1m 30s
build-ubuntu (3.8, Everything else)	3m 53s
build-ubuntu (3.13, Repository only)	1m 47s
build-ubuntu (3.13, Everything else)	3m 12s
build-ubuntu (3.13, lfs)	1m 5s
build-ubuntu (3.8, fastai)	1m 27s
build-ubuntu (3.10, fastai)	51s
build-ubuntu (3.8, tensorflow)	58s
build-ubuntu (3.10, tensorflow)	1m 1s
build-ubuntu (3.8, Python 3.8, torch_1.11)	1m 13s
build-ubuntu (3.12, torch_latest)	1m 1s
	22m 39s

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