test-lib: add a PTHREADS prerequisite

Add a PTHREADS prerequisite which is false when git is compiled with
NO_PTHREADS=YesPlease.

There's lots of custom code that runs when threading isn't available,
but before this prerequisite there was no way to test it.

Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

Makefile

@@ -2242,6 +2242,7 @@ GIT-BUILD-OPTIONS: FORCE
 	@echo NO_EXPAT=\''$(subst ','\'',$(subst ','\'',$(NO_EXPAT)))'\' >>$@+
 	@echo USE_LIBPCRE1=\''$(subst ','\'',$(subst ','\'',$(USE_LIBPCRE)))'\' >>$@+
 	@echo NO_PERL=\''$(subst ','\'',$(subst ','\'',$(NO_PERL)))'\' >>$@+
+	@echo NO_PTHREADS=\''$(subst ','\'',$(subst ','\'',$(NO_PTHREADS)))'\' >>$@+
 	@echo NO_PYTHON=\''$(subst ','\'',$(subst ','\'',$(NO_PYTHON)))'\' >>$@+
 	@echo NO_UNIX_SOCKETS=\''$(subst ','\'',$(subst ','\'',$(NO_UNIX_SOCKETS)))'\' >>$@+
 	@echo PAGER_ENV=\''$(subst ','\'',$(subst ','\'',$(PAGER_ENV)))'\' >>$@+

t/README

@@ -817,6 +817,10 @@ use these, and "test_set_prereq" for how to define your own.
    Test is run on a filesystem which converts decomposed utf-8 (nfd)
    to precomposed utf-8 (nfc).
 
+ - PTHREADS
+
+   Git wasn't compiled with NO_PTHREADS=YesPlease.
+
 Tips for Writing Tests
 ----------------------
 

t/test-lib.sh

@@ -1009,6 +1009,7 @@ esac
 
 ( COLUMNS=1 && test $COLUMNS = 1 ) && test_set_prereq COLUMNS_CAN_BE_1
 test -z "$NO_PERL" && test_set_prereq PERL
+test -z "$NO_PTHREADS" && test_set_prereq PTHREADS
 test -z "$NO_PYTHON" && test_set_prereq PYTHON
 test -n "$USE_LIBPCRE1" && test_set_prereq PCRE
 test -z "$NO_GETTEXT" && test_set_prereq GETTEXT