t6030: make test work with SHA-256

Compute several object ID values instead of hard-coding them, and use
test_oid_to_path to cleanly produce a path for an object.

Note that the bisect code which is tested here remains sensitive to the
hash algorithm in use because it uses the object ID to disambiguate
between two equidistant commits.  Fortunately, SHA-1 and SHA-256
disambiguate identically in the cases we care about, so there is no need
to modify the test to accommodate this situation.  However, if a further
hash algorithm change occurs, this test may require some restructuring.

Signed-off-by: brian m. carlson <sandals@crustytoothpaste.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

t/t6030-bisect-porcelain.sh

@@ -615,6 +615,7 @@ test_expect_success 'broken branch creation' '
 	git add missing/MISSING &&
 	git commit -m "6(broken): Added file that will be deleted" &&
 	git tag BROKEN_HASH6 &&
+	deleted=$(git rev-parse --verify HEAD:missing) &&
 	add_line_into_file "7(broken): second line on a broken branch" hello2 &&
 	git tag BROKEN_HASH7 &&
 	add_line_into_file "8(broken): third line on a broken branch" hello2 &&
@@ -622,12 +623,12 @@ test_expect_success 'broken branch creation' '
 	git rm missing/MISSING &&
 	git commit -m "9(broken): Remove missing file" &&
 	git tag BROKEN_HASH9 &&
-	rm .git/objects/39/f7e61a724187ab767d2e08442d9b6b9dab587d
+	rm .git/objects/$(test_oid_to_path $deleted)
 '
 
 echo "" > expected.ok
 cat > expected.missing-tree.default <<EOF
-fatal: unable to read tree 39f7e61a724187ab767d2e08442d9b6b9dab587d
+fatal: unable to read tree $deleted
 EOF
 
 test_expect_success 'bisect fails if tree is broken on start commit' '
@@ -713,12 +714,12 @@ test_expect_success 'bisect: demonstrate identification of damage boundary' "
 "
 
 cat > expected.bisect-log <<EOF
-# bad: [32a594a3fdac2d57cf6d02987e30eec68511498c] Add <4: Ciao for now> into <hello>.
-# good: [7b7f204a749c3125d5224ed61ea2ae1187ad046f] Add <2: A new day for git> into <hello>.
-git bisect start '32a594a3fdac2d57cf6d02987e30eec68511498c' '7b7f204a749c3125d5224ed61ea2ae1187ad046f'
-# good: [3de952f2416b6084f557ec417709eac740c6818c] Add <3: Another new day for git> into <hello>.
-git bisect good 3de952f2416b6084f557ec417709eac740c6818c
-# first bad commit: [32a594a3fdac2d57cf6d02987e30eec68511498c] Add <4: Ciao for now> into <hello>.
+# bad: [$HASH4] Add <4: Ciao for now> into <hello>.
+# good: [$HASH2] Add <2: A new day for git> into <hello>.
+git bisect start '$HASH4' '$HASH2'
+# good: [$HASH3] Add <3: Another new day for git> into <hello>.
+git bisect good $HASH3
+# first bad commit: [$HASH4] Add <4: Ciao for now> into <hello>.
 EOF
 
 test_expect_success 'bisect log: successful result' '
@@ -731,14 +732,14 @@ test_expect_success 'bisect log: successful result' '
 '
 
 cat > expected.bisect-skip-log <<EOF
-# bad: [32a594a3fdac2d57cf6d02987e30eec68511498c] Add <4: Ciao for now> into <hello>.
-# good: [7b7f204a749c3125d5224ed61ea2ae1187ad046f] Add <2: A new day for git> into <hello>.
-git bisect start '32a594a3fdac2d57cf6d02987e30eec68511498c' '7b7f204a749c3125d5224ed61ea2ae1187ad046f'
-# skip: [3de952f2416b6084f557ec417709eac740c6818c] Add <3: Another new day for git> into <hello>.
-git bisect skip 3de952f2416b6084f557ec417709eac740c6818c
+# bad: [$HASH4] Add <4: Ciao for now> into <hello>.
+# good: [$HASH2] Add <2: A new day for git> into <hello>.
+git bisect start '$HASH4' '$HASH2'
+# skip: [$HASH3] Add <3: Another new day for git> into <hello>.
+git bisect skip $HASH3
 # only skipped commits left to test
-# possible first bad commit: [32a594a3fdac2d57cf6d02987e30eec68511498c] Add <4: Ciao for now> into <hello>.
-# possible first bad commit: [3de952f2416b6084f557ec417709eac740c6818c] Add <3: Another new day for git> into <hello>.
+# possible first bad commit: [$HASH4] Add <4: Ciao for now> into <hello>.
+# possible first bad commit: [$HASH3] Add <3: Another new day for git> into <hello>.
 EOF
 
 test_expect_success 'bisect log: only skip commits left' '