+#define COMMON_DIFF_OPTIONS_HELP \
+"\ncommon diff options:\n" \
+" -r diff recursively (only meaningful in diff-tree)\n" \
+" -z output diff-raw with lines terminated with NUL.\n" \
+" -p output patch format.\n" \
+" -u synonym for -p.\n" \
+" --name-only show only names of changed files.\n" \
+" --name-only-z\n" \
+" same as --name-only but terminate lines with NUL.\n" \
+" -R swap input file pairs.\n" \
+" -B detect complete rewrites.\n" \
+" -M detect renames.\n" \
+" -C detect copies.\n" \
+" --find-copies-harder\n" \
+" try unchanged files as candidate for copy detection.\n" \
+" -O<file> reorder diffs according to the <file>.\n" \
+" -S<string> find filepair whose only one side contains the string.\n" \
+" --pickaxe-all\n" \
+" show all files diff when -S is used and hit is found.\n"
+