reset --hard: skip blank lines when reporting the commit subject

reset --hard: skip blank lines when reporting the commit subject

When there are blank lines at the beginning of a commit message, the
pretty printing machinery already skips them when showing a commit
subject (or the complete commit message). We shall henceforth do the
same when reporting the commit subject after the user called

	git reset --hard <commit>

Signed-off-by: Johannes Schindelin <redacted>
Signed-off-by: Junio C Hamano <redacted>