t4007: abstract away SHA-1-specific constants

Adjust the test so that it computes variables for blobs and uses the
ZERO_OID variable instead of using hard-coded hashes.

Signed-off-by: brian m. carlson <[email protected]>
Signed-off-by: Junio C Hamano <[email protected]>

Author: bk2204

t/t4007-rename-3.sh

@@ -17,6 +17,7 @@ test_expect_success 'prepare reference tree' '
 	echo $tree
 '
 
+blob=$(git hash-object "$TEST_DIRECTORY/diff-lib/COPYING")
 test_expect_success 'prepare work tree' '
 	cp path0/COPYING path1/COPYING &&
 	git update-index --add --remove path0/COPYING path1/COPYING
@@ -26,8 +27,8 @@ test_expect_success 'prepare work tree' '
 # path1 both have COPYING and the latter is a copy of path0/COPYING.
 # Comparing the full tree with cache should tell us so.
 
-cat >expected <<\EOF
-:100644 100644 6ff87c4664981e4397625791c8ea3bbb5f2279a3 6ff87c4664981e4397625791c8ea3bbb5f2279a3 C100	path0/COPYING	path1/COPYING
+cat >expected <<EOF
+:100644 100644 $blob $blob C100	path0/COPYING	path1/COPYING
 EOF
 
 test_expect_success 'copy detection' '
@@ -46,8 +47,8 @@ test_expect_success 'copy detection, cached' '
 # path1/COPYING suddenly appearing from nowhere, not detected as
 # a copy from path0/COPYING.
 
-cat >expected <<\EOF
-:000000 100644 0000000000000000000000000000000000000000 6ff87c4664981e4397625791c8ea3bbb5f2279a3 A	path1/COPYING
+cat >expected <<EOF
+:000000 100644 $ZERO_OID $blob A	path1/COPYING
 EOF
 
 test_expect_success 'copy, limited to a subtree' '
@@ -64,8 +65,8 @@ test_expect_success 'tweak work tree' '
 # path0/COPYING.  Showing the full tree with cache should tell us about
 # the rename.
 
-cat >expected <<\EOF
-:100644 100644 6ff87c4664981e4397625791c8ea3bbb5f2279a3 6ff87c4664981e4397625791c8ea3bbb5f2279a3 R100	path0/COPYING	path1/COPYING
+cat >expected <<EOF
+:100644 100644 $blob $blob R100	path0/COPYING	path1/COPYING
 EOF
 
 test_expect_success 'rename detection' '
@@ -78,8 +79,8 @@ test_expect_success 'rename detection' '
 # path0/COPYING.  When we say we care only about path1, we should just
 # see path1/COPYING appearing from nowhere.
 
-cat >expected <<\EOF
-:000000 100644 0000000000000000000000000000000000000000 6ff87c4664981e4397625791c8ea3bbb5f2279a3 A	path1/COPYING
+cat >expected <<EOF
+:000000 100644 $ZERO_OID $blob A	path1/COPYING
 EOF
 
 test_expect_success 'rename, limited to a subtree' '