Merge branch 'js/perf-on-apple' into maint

t/perf needs /usr/bin/time with GNU extension; the invocation of it
is updated to "gtime" on Darwin.

* js/perf-on-apple:
  perf: accommodate for MacOSX

.travis.yml

@@ -82,6 +82,8 @@ before_install:
       brew tap homebrew/binary --quiet
       brew_force_set_latest_binary_hash perforce
       brew_force_set_latest_binary_hash perforce-server
+      # Uncomment this if you want to run perf tests:
+      # brew install gnu-time
       brew install git-lfs perforce-server perforce gettext
       brew link --force gettext
       ;;

t/perf/perf-lib.sh

@@ -127,11 +127,15 @@ test_checkout_worktree () {
 # Performance tests should never fail.  If they do, stop immediately
 immediate=t
 
+# Perf tests require GNU time
+case "$(uname -s)" in Darwin) GTIME="${GTIME:-gtime}";; esac
+GTIME="${GTIME:-/usr/bin/time}"
+
 test_run_perf_ () {
 	test_cleanup=:
 	test_export_="test_cleanup"
 	export test_cleanup test_export_
-	/usr/bin/time -f "%E %U %S" -o test_time.$i "$SHELL" -c '
+	"$GTIME" -f "%E %U %S" -o test_time.$i "$SHELL" -c '
 . '"$TEST_DIRECTORY"/test-lib-functions.sh'
 test_export () {
 	[ $# != 0 ] || return 0