test: use $_z40 from test-lib

There is no need to duplicate the definition of $_z40 and $_x40 that
test-lib.sh supplies the test scripts.

Signed-off-by: Junio C Hamano <gitster@pobox.com>

t/t1400-update-ref.sh

@@ -6,7 +6,7 @@
 test_description='Test git update-ref and basic ref logging'
 . ./test-lib.sh
 
-Z=0000000000000000000000000000000000000000
+Z=$_z40
 
 test_expect_success setup '
 

t/t1501-worktree.sh

@@ -7,7 +7,6 @@ test_expect_success 'setup' '
 	EMPTY_TREE=$(git write-tree) &&
 	EMPTY_BLOB=$(git hash-object -t blob --stdin </dev/null) &&
 	CHANGED_BLOB=$(echo changed | git hash-object -t blob --stdin) &&
-	ZEROES=0000000000000000000000000000000000000000 &&
 	EMPTY_BLOB7=$(echo $EMPTY_BLOB | sed "s/\(.......\).*/\1/") &&
 	CHANGED_BLOB7=$(echo $CHANGED_BLOB | sed "s/\(.......\).*/\1/") &&
 
@@ -239,10 +238,10 @@ test_expect_success '_gently() groks relative GIT_DIR & GIT_WORK_TREE' '
 
 test_expect_success 'diff-index respects work tree under .git dir' '
 	cat >diff-index-cached.expected <<-EOF &&
-	:000000 100644 $ZEROES $EMPTY_BLOB A	sub/dir/tracked
+	:000000 100644 $_z40 $EMPTY_BLOB A	sub/dir/tracked
 	EOF
 	cat >diff-index.expected <<-EOF &&
-	:000000 100644 $ZEROES $ZEROES A	sub/dir/tracked
+	:000000 100644 $_z40 $_z40 A	sub/dir/tracked
 	EOF
 
 	(
@@ -258,7 +257,7 @@ test_expect_success 'diff-index respects work tree under .git dir' '
 
 test_expect_success 'diff-files respects work tree under .git dir' '
 	cat >diff-files.expected <<-EOF &&
-	:100644 100644 $EMPTY_BLOB $ZEROES M	sub/dir/tracked
+	:100644 100644 $EMPTY_BLOB $_z40 M	sub/dir/tracked
 	EOF
 
 	(

t/t2011-checkout-invalid-head.sh

@@ -15,7 +15,7 @@ test_expect_success 'checkout should not start branch from a tree' '
 '
 
 test_expect_success 'checkout master from invalid HEAD' '
-	echo 0000000000000000000000000000000000000000 >.git/HEAD &&
+	echo $_z40 >.git/HEAD &&
 	git checkout master --
 '
 

t/t2201-add-update-typechange.sh

@@ -4,8 +4,6 @@ test_description='more git add -u'
 
 . ./test-lib.sh
 
-_z40=0000000000000000000000000000000000000000
-
 test_expect_success setup '
 	>xyzzy &&
 	_empty=$(git hash-object --stdin <xyzzy) &&

t/t3200-branch.sh

@@ -35,7 +35,7 @@ test_expect_success \
     'git branch a/b/c && test -f .git/refs/heads/a/b/c'
 
 cat >expect <<EOF
-0000000000000000000000000000000000000000 $HEAD $GIT_COMMITTER_NAME <$GIT_COMMITTER_EMAIL> 1117150200 +0000	branch: Created from master
+$_z40 $HEAD $GIT_COMMITTER_NAME <$GIT_COMMITTER_EMAIL> 1117150200 +0000	branch: Created from master
 EOF
 test_expect_success \
     'git branch -l d/e/f should create a branch and a log' \
@@ -214,7 +214,7 @@ test_expect_success \
 
 # Keep this test last, as it changes the current branch
 cat >expect <<EOF
-0000000000000000000000000000000000000000 $HEAD $GIT_COMMITTER_NAME <$GIT_COMMITTER_EMAIL> 1117150200 +0000	branch: Created from master
+$_z40 $HEAD $GIT_COMMITTER_NAME <$GIT_COMMITTER_EMAIL> 1117150200 +0000	branch: Created from master
 EOF
 test_expect_success \
     'git checkout -b g/h/i -l should create a branch and a log' \

t/t3600-rm.sh

@@ -240,11 +240,10 @@ test_expect_success 'refresh index before checking if it is up-to-date' '
 
 test_expect_success 'choking "git rm" should not let it die with cruft' '
 	git reset -q --hard &&
-	H=0000000000000000000000000000000000000000 &&
 	i=0 &&
 	while test $i -lt 12000
 	do
-	    echo "100644 $H 0	some-file-$i"
+	    echo "100644 $_z40 0	some-file-$i"
 	    i=$(( $i + 1 ))
 	done | git update-index --index-info &&
 	git rm -n "some-file-*" | :;

t/t4002-diff-basic.sh

@@ -126,15 +126,12 @@ cat >.test-recursive-AB <<\EOF
 :100644 100644 3fdbe17fd013303a2e981e1ca1c6cd6e72789087 7e09d6a3a14bd630913e8c75693cea32157b606d M	Z/NM
 EOF
 
-x40='[0-9a-f][0-9a-f][0-9a-f][0-9a-f][0-9a-f]'
-x40="$x40$x40$x40$x40$x40$x40$x40$x40"
-z40='0000000000000000000000000000000000000000'
 cmp_diff_files_output () {
     # diff-files never reports additions.  Also it does not fill in the
     # object ID for the changed files because it wants you to look at the
     # filesystem.
     sed <"$2" >.test-tmp \
-	-e '/^:000000 /d;s/'$x40'\( [MCRNDU][0-9]*\)	/'$z40'\1	/' &&
+	-e '/^:000000 /d;s/'$_x40'\( [MCRNDU][0-9]*\)	/'$_z40'\1	/' &&
     test_cmp "$1" .test-tmp
 }
 

t/t4020-diff-external.sh

@@ -4,8 +4,6 @@ test_description='external diff interface test'
 
 . ./test-lib.sh
 
-_z40=0000000000000000000000000000000000000000
-
 test_expect_success setup '
 
 	test_tick &&

t/t4027-diff-submodule.sh

@@ -5,7 +5,6 @@ test_description='difference in submodules'
 . ./test-lib.sh
 . "$TEST_DIRECTORY"/diff-lib.sh
 
-_z40=0000000000000000000000000000000000000000
 test_expect_success setup '
 	test_tick &&
 	test_create_repo sub &&

t/t7011-skip-worktree-reading.sh

@@ -24,7 +24,7 @@ H sub/2
 EOF
 
 NULL_SHA1=e69de29bb2d1d6434b8b29ae775ad8c2e48c5391
-ZERO_SHA0=0000000000000000000000000000000000000000
+
 setup_absent() {
 	test -f 1 && rm 1
 	git update-index --remove 1 &&
@@ -120,7 +120,7 @@ test_expect_success 'grep with skip-worktree file' '
 	test "$(git grep --no-ext-grep test)" = "1:test"
 '
 
-echo ":000000 100644 $ZERO_SHA0 $NULL_SHA1 A	1" > expected
+echo ":000000 100644 $_z40 $NULL_SHA1 A	1" > expected
 test_expect_success 'diff-index does not examine skip-worktree absent entries' '
 	setup_absent &&
 	git diff-index HEAD -- 1 > result &&

t/t7012-skip-worktree-writing.sh

@@ -54,7 +54,7 @@ test_expect_success 'read-tree removes worktree, dirty case' '
 '
 
 NULL_SHA1=e69de29bb2d1d6434b8b29ae775ad8c2e48c5391
-ZERO_SHA0=0000000000000000000000000000000000000000
+
 setup_absent() {
 	test -f 1 && rm 1
 	git update-index --remove 1 &&

t/test-lib.sh

@@ -97,6 +97,9 @@ esac
 _x05='[0-9a-f][0-9a-f][0-9a-f][0-9a-f][0-9a-f]'
 _x40="$_x05$_x05$_x05$_x05$_x05$_x05$_x05$_x05"
 
+# Zero SHA-1
+_z40=0000000000000000000000000000000000000000
+
 # Each test should start with something like this, after copyright notices:
 #
 # test_description='Description of this test...