I think it's better that skip checking when "staged_files" is empty array.
# If staged_files is empty, following git command execute
# So every staged files are checked even if they are written in .pre_commit.ignore
git diff-index --check --cached HEAD -- 2>&1
Coverage increased (+0.0%) to 98.65% when pulling ef96369f616c5ff8225b19c534f96afb0150a89a on TakiTake:skip_checking_when_staged_files_are_empty into 6840a5eed38f4b88d27b0b4c158dbaf522750899 on jish:master.
I think it's better that skip checking when "staged_files" is empty array.