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/lib-rebase.sh

@@ -44,10 +44,10 @@ set_fake_editor () {
 	rm -f "$1"
 	echo 'rebase -i script before editing:'
 	cat "$1".tmp
-	action=\&
+	action=pick
 	for line in $FAKE_LINES; do
 		case $line in
-		pick|p|squash|s|fixup|f|edit|e|reword|r|drop|d|label|l|reset|r|merge|m)
+		pick|p|squash|s|fixup|f|edit|e|reword|r|drop|d)
 			action="$line";;
 		exec_*|x_*|break|b)
 			echo "$line" | sed 's/_/ /g' >> "$1";;
@@ -58,12 +58,11 @@ set_fake_editor () {
 		bad)
 			action="badcmd";;
 		fakesha)
-			test \& != "$action" || action=pick
 			echo "$action XXXXXXX False commit" >> "$1"
 			action=pick;;
 		*)
-			sed -n "${line}s/^[a-z][a-z]*/$action/p" < "$1".tmp >> "$1"
-			action=\&;;
+			sed -n "${line}s/^pick/$action/p" < "$1".tmp >> "$1"
+			action=pick;;
 		esac
 	done
 	echo 'rebase -i script after editing:'
@@ -119,31 +118,3 @@ make_empty () {
 	git commit --allow-empty -m "$1" &&
 	git tag "$1"
 }
-
-# Call this (inside test_expect_success) at the end of a test file to
-# check that no tests have changed editor related environment
-# variables or config settings
-test_editor_unchanged () {
-	# We're only interested in exported variables hence 'sh -c'
-	sh -c 'cat >actual <<-EOF
-	EDITOR=$EDITOR
-	FAKE_COMMIT_AMEND=$FAKE_COMMIT_AMEND
-	FAKE_COMMIT_MESSAGE=$FAKE_COMMIT_MESSAGE
-	FAKE_LINES=$FAKE_LINES
-	GIT_EDITOR=$GIT_EDITOR
-	GIT_SEQUENCE_EDITOR=$GIT_SEQUENCE_EDITOR
-	core.editor=$(git config core.editor)
-	sequence.editor=$(git config sequence.editor)
-	EOF'
-	cat >expect <<-\EOF
-	EDITOR=:
-	FAKE_COMMIT_AMEND=
-	FAKE_COMMIT_MESSAGE=
-	FAKE_LINES=
-	GIT_EDITOR=
-	GIT_SEQUENCE_EDITOR=
-	core.editor=
-	sequence.editor=
-	EOF
-	test_cmp expect actual
-}