Optionally work without python

In some setups (notably server setups) you do not need that dependency.
Gracefully handle the absence of python when NO_PYTHON is defined.

Signed-off-by: Johannes E. Schindelin <Johannes.Schindelin@gmx.de>
Signed-off-by: Junio C Hamano <junkio@cox.net>

t/Makefile

@@ -15,6 +15,10 @@ shellquote = '$(call shq,$(1))'
 
 T = $(wildcard t[0-9][0-9][0-9][0-9]-*.sh)
 
+ifdef NO_PYTHON
+	GIT_TEST_OPTS += --no-python
+endif
+
 all: $(T) clean
 
 $(T):

t/t0000-basic.sh

@@ -42,7 +42,7 @@ fi
 
 . ./test-lib.sh
 
-"$PYTHON" -c 'import subprocess' || {
+test "$no_python" || "$PYTHON" -c 'import subprocess' || {
 	echo >&2 'Your python seem to lack "subprocess" module.
 Please check INSTALL document.'
 	exit 1

t/t6021-merge-criss-cross.sh

@@ -10,6 +10,12 @@
 test_description='Test criss-cross merge'
 . ./test-lib.sh
 
+if test "$no_python"; then
+	echo "Skipping: no python => no recursive merge"
+	test_done
+	exit 0
+fi
+
 test_expect_success 'prepare repository' \
 'echo "1
 2

t/t6022-merge-rename.sh

@@ -3,6 +3,12 @@
 test_description='Merge-recursive merging renames'
 . ./test-lib.sh
 
+if test "$no_python"; then
+	echo "Skipping: no python => no recursive merge"
+	test_done
+	exit 0
+fi
+
 test_expect_success setup \
 '
 cat >A <<\EOF &&

t/test-lib.sh

@@ -63,6 +63,8 @@ do
 		exit 0 ;;
 	-v|--v|--ve|--ver|--verb|--verbo|--verbos|--verbose)
 		verbose=t; shift ;;
+	--no-python)
+		no_python=t; shift ;;
 	*)
 		break ;;
 	esac