Run Tools/scripts/mfh through devel/hs-ShellCheck.

SC2068: Double quote array expansions to avoid re-splitting elements.
SC2034: revs appears unused. Verify it or export it.
SC2039: In POSIX sh, XXX is undefined.

type     -> command -v
echo -n  -> printf
read -p  -> printf + read

SC2162: read without -r will mangle backslashes.
SC2086: Double quote to prevent globbing and word splitting.

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