reviewdog_flags options does not work

[hugo-syn]

Hi I'm having issues with the reviewdog_flags option. I've added: reviewdog_flags: '--diff="git diff HEAD^"' but it doesn't work.

I get:
reviewdog: invalid command line string

And If I add quotes in the entrypoint.sh for the INPUT_REVIEWDOG_FLAGS variable I get:
reviewdog: fail to get diff: exec: "git diff HEAD^": executable file not found in $PATH

Any suggestion ?