t3404: remove uneeded calls to set_fake_editor

Some tests were calling set_fake_editor to ensure they had a sane no-op
editor set. Now that all the editor setting is done in subshells these
tests can rely on EDITOR=: and so do not need to call set_fake_editor.

Also add a test at the end to detect any future additions messing with
the exported value of $EDITOR.

Signed-off-by: Phillip Wood <phillip.wood@dunelm.org.uk>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

t/lib-rebase.sh

@@ -118,3 +118,31 @@ 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
+}