Add support for macOS catalina date (#300)

Co-authored-by: Benoit Sagols <[email protected]>

tests/test-lib.sh

@@ -495,19 +495,12 @@ test_init_todo () {
 	#...
 	if date --version 2>&1 | grep -q "GNU"; then
 		DATE_STYLE=GNU
-	# on Mac OS X 10.15:
-	#date --version
-	#date: illegal option -- -
-	#usage: date [-jnRu] [-d dst] [-r seconds] [-t west] [-v[+|-]val[ymwdHMS]] ...
-	#            [-f fmt date | [[[mm]dd]HH]MM[[cc]yy][.ss]] [+format]
-	elif date --version 2>&1 | grep -q -e "-jnRu"; then
-		DATE_STYLE=Mac10.15
 	# on Mac OS X 10.5:
 	#date --version
 	#date: illegal option -- -
 	#usage: date [-jnu] [-d dst] [-r seconds] [-t west] [-v[+|-]val[ymwdHMS]] ...
 	#            [-f fmt date | [[[mm]dd]HH]MM[[cc]yy][.ss]] [+format]
-	elif date --version 2>&1 | grep -q -e "-jnu"; then
+	elif date --version 2>&1 | grep -q -e "-jnR\?u"; then
 		DATE_STYLE=Mac10.5
 	# on Mac OS X 10.4:
 	#date --version
@@ -526,13 +519,6 @@ test_init_todo () {
 			EOF
 			chmod 755 bin/date
 		;;
-		Mac10.15)
-			cat > bin/date <<-EOF
-			#!/bin/sh
-			exec "$TODO_TEST_REAL_DATE" -j -f %s \$TODO_TEST_TIME \$@
-			EOF
-			chmod 755 bin/date
-		;;
 		Mac10.5)
 			cat > bin/date <<-EOF
 			#!/bin/sh