add -h and --dfsg options to tests

Use getopt(1) to provide -h, --help, and --dfsg options in
test/fetch-test-deps.sh and test/run-tests.sh

- -h or --help prints a usage message
- --dfsg skips repositories with non-free licenses (pokecrystal
  and pokered) in favor of ucity to support packaging RGBDS for
  Debian
- --dfsg can be combined with --get-hash or --get-paths

change --dfsg option to --only-free

I was told the `+dfsg.1` used in Debian's repacks of upstream repos
and tarballs that contain non-free software is too obscure.  ISSOtm
and Rangi42 suggested `--only-free` which carries no Debian baggage.
https://www.reddit.com/r/debian/comments/66094l/what_is_dfsg_in_package_version_numbers/

- change --dfsg option to --only-free
- temporarily enable logging (set -x) to troubleshoot build failure
  on macOS

don't depend on util-linux getopt

util-linux getopt has long option parsing functionality not
available in macOS getopt.  Instead, parse the options in pure
Bash, treating each option as a separate word.

remove tracing from test

The removal of getopt indeed fixed test scripts on macOS.
This means we no longer need set -x to trace execution.

Co-authored-by: Eldred Habert <[email protected]>

use true/false for booleans in test scripts

I haven't had a chance to read the `bash(1)` manual cover to cover
(reading 6600 lines in `less(1)` is an attention challenge to me)
but it appears `true` and `false` are preferred because `true(1)`
and `false(1)` run faster than `test(1)`, to which `[` is a link.

Co-authored-by: Eldred Habert <[email protected]>

act on stylistic nitpicks by Rangi42

- remove explanation of `set -e` even from run-tests.sh, which had
  previously included one
- visually distinguish explanations of sections of a script from
  explanations of individual functions within a section
- change variable names that refer to script names to match the
  capitalized default filename of the script minus any extension
- change variable names that do not refer to script names to
  lowercase

Apply suggestions from code review

Co-authored-by: Rangi <[email protected]>

remane with_nonfree variable in tests to nonfree

per @Rangi42's preference

test/fetch-test-deps.sh

@@ -1,10 +1,45 @@
 #!/usr/bin/env bash
-
 set -e
 
 cd "$(dirname "$0")"
 
-case "$1" in
+usage() {
+	echo "Downloads source code of Game Boy programs used as RGBDS test cases."
+	echo "Options:"
+	echo "    -h, --help      show this help message"
+	echo "    --only-free     download only freely licensed codebases"
+	echo "    --get-hash      print programs' commit hashes instead of downloading them"
+	echo "    --get-paths     print programs' GitHub paths instead of downloading them"
+}
+
+# Parse options in pure Bash because macOS `getopt` is stuck
+# in what util-linux `getopt` calls `GETOPT_COMPATIBLE` mode
+nonfree=true
+actionname=
+while [[ $# -gt 0 ]]; do
+	case "$1" in
+		-h|--help)
+			usage
+			exit 0
+			;;
+		--only-free)
+			nonfree=false
+			;;
+		--get-hash|--get-paths)
+			actionname="$1"
+			;;
+		--)
+			break
+			;;
+		*)
+			echo "$(basename $0): unknown option "$1""
+			exit 1
+			;;
+	esac
+	shift
+done
+
+case "$actionname" in
 	--get-hash)
 		action() { # owner/repo shallow-since commit
 			printf "%s@%s-" "${1##*/}" "$3"
@@ -33,6 +68,8 @@ case "$1" in
 		}
 esac
 
-action pret/pokecrystal 2022-09-29 70a3ec1accb6de1c1c273470af0ddfa2edc1b0a9
-action pret/pokered     2022-09-29 2b52ceb718b55dce038db24d177715ae4281d065
-action AntonioND/ucity  2022-04-20 d8878233da7a6569f09f87b144cb5bf140146a0f
+if "$nonfree"; then
+	action pret/pokecrystal 2022-09-29 70a3ec1accb6de1c1c273470af0ddfa2edc1b0a9
+	action pret/pokered     2022-09-29 2b52ceb718b55dce038db24d177715ae4281d065
+fi
+action         AntonioND/ucity  2022-04-20 d8878233da7a6569f09f87b144cb5bf140146a0f

test/run-tests.sh

@@ -1,11 +1,40 @@
 #!/usr/bin/env bash
-
-# Return failure as soon as a command fails to execute
-
 set -e
 
 cd "$(dirname "$0")"
 
+usage() {
+	echo "Runs regression tests on RGBDS."
+	echo "Options:"
+	echo "    -h, --help      show this help message"
+	echo "    --only-free     skip tests that build nonfree codebases"
+}
+
+# Parse options in pure Bash because macOS `getopt` is stuck
+# in what util-linux `getopt` calls `GETOPT_COMPATIBLE` mode
+nonfree=true
+FETCH_TEST_DEPS="fetch-test-deps.sh"
+while [[ $# -gt 0 ]]; do
+	case "$1" in
+		-h|--help)
+			usage
+			exit 0
+			;;
+		--only-free)
+			nonfree=false
+			FETCH_TEST_DEPS="fetch-test-deps.sh --only-free"
+			;;
+		--)
+			break
+			;;
+		*)
+			echo "$(basename $0): internal error"
+			exit 1
+			;;
+	esac
+	shift
+done
+
 # Refuse to run if RGBDS isn't present
 if [[ ! ( -x ../rgbasm && -x ../rgblink && -x ../rgbfix && -x ../rgbgfx ) ]]; then
 	echo "Please build RGBDS before running the tests"
@@ -27,14 +56,16 @@ done
 
 test_downstream() { # owner/repo make-target
 	if ! pushd ${1##*/}; then
-		echo >&2 'Please run `fetch-test-deps.sh` before running the test suite'
+		echo >&2 'Please run `'"$FETCH_TEST_DEPS"'` before running the test suite'
 		return 1
 	fi
 	make clean
 	make -j4 $2 RGBDS=../../
 	popd
 }
 
-test_downstream pret/pokecrystal compare
-test_downstream pret/pokered     compare
+if "$nonfree"; then
+	test_downstream pret/pokecrystal compare
+	test_downstream pret/pokered     compare
+fi
 test_downstream AntonioND/ucity  ''