build: Add doctest make target

Running `make doctest` will make sure the manual page is synchronized with the
available options.

Makefile

@@ -1,6 +1,6 @@
 all: svtplay-dl
 
-.PHONY: test cover pylint svtplay-dl
+.PHONY: test cover doctest pylint svtplay-dl
 
 VERSION = 0.10.$(shell date +%Y.%m.%d)
 
@@ -53,6 +53,9 @@ cover:
 pylint:
 	$(MAKE) -C lib pylint
 
+doctest: svtplay-dl
+	sh scripts/diff_man_help.sh
+
 clean:
 	$(MAKE) -C lib clean
 	rm -f svtplay-dl

scripts/diff_man_help.sh

@@ -1,7 +1,5 @@
 #!/bin/sh
 # Make sure the options listed in --help and the manual are in sync.
-diff_opts="$@"
-diff_opts=${diff_opts:-"-u"}
 TMPDIR=$(mktemp -d svtplay-man-test-XXXXXX)
 [ "$TMPDIR" ] || {
 	echo "mktemp not available, using static dir"
@@ -35,6 +33,7 @@ for file in $TMPDIR/options.*; do
 	perl -i -pe 's/^(-.(?: [^-][^ ]+)?) (--.*)/\2 \1/' $file
 done
 
-# There should be no difference.
-diff $diff_opts $TMPDIR/options.*
-#sha1sum $TMPDIR/options.*
+[ "$(sha1sum<$TMPDIR/options.help)" = "$(sha1sum<$TMPDIR/options.man)" ] || {
+	diff -u $TMPDIR/options.help $TMPDIR/options.man
+	exit 1
+}