t6038: make tests fail for the right reason

t6038: make tests fail for the right reason

t6038 had a pair of tests that were expected to fail, but weren't
failing for the expected reason.  Both were meant to do a merge that
could be done cleanly after renormalization, but were supposed to fail
for lack of renormalization.  Unfortunately, both tests had staged
changes, and checkout -m would abort due to the presence of those staged
changes before even attempting a merge.

Fix this first issue by utilizing git-restore instead of git-checkout,
so that the index is left alone and just the working directory gets the
changes we want.

However, there is a second issue with these tests.  Technically, they
just wanted to verify that after renormalization, no conflicts would be
present.  This could have been checked for by grepping for a lack of
conflict markers, but the test instead tried to compare the working
directory files to an expected result.  Unfortunately, the setting of
"text=auto" without setting core.eol to any value meant that the content
of the file (in particular, the line endings) would be
platform-dependent and the tests could only pass on some platforms.
Replace the existing comparison with a call to 'git diff --no-index
--ignore-cr-at-eol' to verify that the contents, other than possible
carriage returns in the file, match the expected results and in
particular that the file has no conflicts from the checkout -m
operation.

Signed-off-by: Elijah Newren <redacted>
Signed-off-by: Junio C Hamano <redacted>