git-base: Use bash to run tests

At least with NetBSD (9.99.17) sh(1) the `streaming support for --stdin'
test hangs.  Force to use bash for tests.

Index: Makefile
===================================================================
RCS file: /cvsroot/pkgsrc/devel/git-base/Makefile,v
retrieving revision 1.72
diff -u -p -r1.72 Makefile
--- Makefile	10 Dec 2019 18:32:38 -0000	1.72
+++ Makefile	11 Dec 2019 13:42:49 -0000
@@ -15,7 +15,7 @@ DEPENDS+=	p5-Net-SMTP-SSL>=1.01:../../ma
 DEPENDS+=	p5-Authen-SASL>=1.0:../../security/p5-Authen-SASL
 
 USE_LANGUAGES=		c99
-USE_TOOLS+=		perl:run sh:run msgfmt
+USE_TOOLS+=		perl:run sh:run msgfmt bash:test
 
 REPLACE_PERL+=		*.perl */*.perl */*/*.perl
 REPLACE_PERL+=		contrib/hooks/update-paranoid
@@ -82,6 +82,12 @@ SUBST_STAGE.fix-cd-P=	pre-build
 SUBST_SED.fix-cd-P=	-e "s/cd -P/cd/g"
 .endif
 
+SUBST_CLASSES+=			test-shell
+SUBST_FILES.test-shell=		t/Makefile
+SUBST_MESSAGE.test-shell=	Use bash as TEST_SHELL_PATH
+SUBST_STAGE.test-shell=		pre-build
+SUBST_SED.test-shell=		-e '/^TEST_SHELL_PATH/ s;$$(SHELL_PATH);${TOOLS_BASH};'
+
 LDFLAGS.SunOS+=		-lintl -lnsl
 
 .include "../../mk/compiler.mk"