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>

Makefile

@@ -58,6 +58,8 @@ all:
 # Define NO_ACCURATE_DIFF if your diff program at least sometimes misses
 # a missing newline at the end of the file.
 #
+# Define NO_PYTHON if you want to loose all benefits of the recursive merge.
+#
 # Define COLLISION_CHECK below if you believe that SHA1's
 # 1461501637330902918203684832716283019655932542976 hashes do not give you
 # sufficient guarantee that no collisions between objects will ever happen.
@@ -442,6 +444,7 @@ $(patsubst %.sh,%,$(SCRIPT_SH)) : % : %.sh
 	sed -e '1s|#!.*/sh|#!$(call shq,$(SHELL_PATH))|' \
 	    -e 's/@@GIT_VERSION@@/$(GIT_VERSION)/g' \
 	    -e 's/@@NO_CURL@@/$(NO_CURL)/g' \
+	    -e 's/@@NO_PYTHON@@/$(NO_PYTHON)/g' \
 	    $@.sh >$@
 	chmod +x $@
 
@@ -521,6 +524,12 @@ doc:
 
 ### Testing rules
 
+# GNU make supports exporting all variables by "export" without parameters.
+# However, the environment gets quite big, and some programs have problems
+# with that.
+
+export NO_PYTHON
+
 test: all
 	$(MAKE) -C t/ all
 

git-merge.sh

@@ -13,6 +13,10 @@ LF='
 all_strategies='recursive octopus resolve stupid ours'
 default_strategies='recursive'
 use_strategies=
+if test "@@NO_PYTHON@@"; then
+	all_strategies='resolve octopus stupid ours'
+	default_strategies='resolve'
+fi
 
 dropsave() {
 	rm -f -- "$GIT_DIR/MERGE_HEAD" "$GIT_DIR/MERGE_MSG" \

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