test-lib: Replace uses of $(expr ...) by POSIX shell features.

In particular:

- Test case counting can be achieved by arithmetic expansion.

- The name of the test, e.g. t1234, can be computed with ${0%%} and ${0##}.
Signed-off-by: NJohannes Sixt <j6t@kdbg.org>

t/test-lib.sh

@@ -242,14 +242,14 @@ test_merge () {
 # the text_expect_* functions instead.
 
 test_ok_ () {
-	test_count=$(expr "$test_count" + 1)
-	test_success=$(expr "$test_success" + 1)
+	test_count=$(($test_count + 1))
+	test_success=$(($test_success + 1))
 	say_color "" "  ok $test_count: $@"
 }
 
 test_failure_ () {
-	test_count=$(expr "$test_count" + 1)
-	test_failure=$(expr "$test_failure" + 1);
+	test_count=$(($test_count + 1))
+	test_failure=$(($test_failure + 1))
 	say_color error "FAIL $test_count: $1"
 	shift
 	echo "$@" | sed -e 's/^/	/'
@@ -257,13 +257,13 @@ test_failure_ () {
 }
 
 test_known_broken_ok_ () {
-	test_count=$(expr "$test_count" + 1)
+	test_count=$(($test_count+1))
 	test_fixed=$(($test_fixed+1))
 	say_color "" "  FIXED $test_count: $@"
 }
 
 test_known_broken_failure_ () {
-	test_count=$(expr "$test_count" + 1)
+	test_count=$(($test_count+1))
 	test_broken=$(($test_broken+1))
 	say_color skip "  still broken $test_count: $@"
 }
@@ -279,12 +279,10 @@ test_run_ () {
 }
 
 test_skip () {
-	this_test=$(expr "./$0" : '.*/\(t[0-9]*\)-[^/]*$')
-	this_test="$this_test.$(expr "$test_count" + 1)"
 	to_skip=
 	for skp in $GIT_SKIP_TESTS
 	do
-		case "$this_test" in
+		case $this_test.$(($test_count+1)) in
 		$skp)
 			to_skip=t
 		esac
@@ -292,7 +290,7 @@ test_skip () {
 	case "$to_skip" in
 	t)
 		say_color skip >&3 "skipping test: $@"
-		test_count=$(expr "$test_count" + 1)
+		test_count=$(($test_count+1))
 		say_color skip "skip $test_count: $1"
 		: true
 		;;
@@ -370,7 +368,7 @@ test_external () {
 	then
 		# Announce the script to reduce confusion about the
 		# test output that follows.
-		say_color "" " run $(expr "$test_count" + 1): $descr ($*)"
+		say_color "" " run $(($test_count+1)): $descr ($*)"
 		# Run command; redirect its stderr to &4 as in
 		# test_run_, but keep its stdout on our stdout even in
 		# non-verbose mode.
@@ -613,7 +611,8 @@ test_create_repo "$test"
 # in subprocesses like git equals our $PWD (for pathname comparisons).
 cd -P "$test" || exit 1
 
-this_test=$(expr "./$0" : '.*/\(t[0-9]*\)-[^/]*$')
+this_test=${0##*/}
+this_test=${this_test%%-*}
 for skp in $GIT_SKIP_TESTS
 do
 	to_skip=