dune

(rule
 (targets merge-fmt-help.txt)
 (deps ./src/merge_fmt.exe)
 (mode promote)
 (action
  (with-stdout-to
   %{targets}
   (run ./src/merge_fmt.exe --help=plain))))

(rule
 (targets merge-fmt-mergetool-help.txt)
 (deps ./src/merge_fmt.exe)
 (mode promote)
 (action
  (with-stdout-to
   %{targets}
   (run ./src/merge_fmt.exe mergetool --help=plain))))

(rule
 (targets merge-fmt-setup-mergetool-help.txt)
 (deps ./src/merge_fmt.exe)
 (mode promote)
 (action
  (with-stdout-to
   %{targets}
   (run ./src/merge_fmt.exe setup-mergetool --help=plain))))

(rule
 (targets merge-fmt-setup-merge-help.txt)
 (deps ./src/merge_fmt.exe)
 (mode promote)
 (action
  (with-stdout-to
   %{targets}
   (run ./src/merge_fmt.exe setup-merge --help=plain))))