revert(3p/git): Revert merge of git upstream at v2.26.2

This causes cgit to serve error pages, which is undesirable.

This reverts commit 5229c9b232, reversing
changes made to f2b211131f.

third_party/git/t/t4027-diff-submodule.sh

@@ -6,7 +6,6 @@ test_description='difference in submodules'
 . "$TEST_DIRECTORY"/diff-lib.sh
 
 test_expect_success setup '
-	test_oid_init &&
 	test_tick &&
 	test_create_repo sub &&
 	(
@@ -37,8 +36,7 @@ test_expect_success setup '
 '
 
 test_expect_success 'git diff --raw HEAD' '
-	hexsz=$(test_oid hexsz) &&
-	git diff --raw --abbrev=$hexsz HEAD >actual &&
+	git diff --raw --abbrev=40 HEAD >actual &&
 	test_cmp expect actual
 '
 
@@ -247,21 +245,23 @@ test_expect_success 'git diff (empty submodule dir)' '
 '
 
 test_expect_success 'conflicted submodule setup' '
-	c=$(test_oid ff_1) &&
+
+	# 39 efs
+	c=fffffffffffffffffffffffffffffffffffffff &&
 	(
 		echo "000000 $ZERO_OID 0	sub" &&
 		echo "160000 1$c 1	sub" &&
 		echo "160000 2$c 2	sub" &&
 		echo "160000 3$c 3	sub"
 	) | git update-index --index-info &&
-	echo >expect.nosub "diff --cc sub
+	echo >expect.nosub '\''diff --cc sub
 index 2ffffff,3ffffff..0000000
 --- a/sub
 +++ b/sub
 @@@ -1,1 -1,1 +1,1 @@@
-- Subproject commit 2$c
- -Subproject commit 3$c
-++Subproject commit $ZERO_OID" &&
+- Subproject commit 2fffffffffffffffffffffffffffffffffffffff
+ -Subproject commit 3fffffffffffffffffffffffffffffffffffffff
+++Subproject commit 0000000000000000000000000000000000000000'\'' &&
 
 	hh=$(git rev-parse HEAD) &&
 	sed -e "s/$ZERO_OID/$hh/" expect.nosub >expect.withsub