Modernized the test script t/lib-read-tree-m-3way.

Comparing to v1:
1. Kept the test title's double quotes if the title needs to 
    be interpolated.
    e.g. in the following block

    -	test_expect_success \
    -	    "adding test file $p and Z/$p" \
    -	    'git update-index --add $p &&
    -	    git update-index --add Z/$p'
    +	test_expect_success "adding test file $p and Z/$p" '
    +	    git update-index --add $p &&
    +	    git update-index --add Z/$p
    +    '

    where the title "adding test file $p and Z/$p" is kept
    to use double quotes, since the "$p" needs to be interpolated.

2. Added a commit to replace spaces with tabs.

Shaoxuan Yuan (2):
  t/lib-read-tree-m-3way: replace double quotes with single quotes
  t/lib-read-tree-m-3way: replace spaces with tabs

 t/lib-read-tree-m-3way.sh | 168 +++++++++++++++++++-------------------
 1 file changed, 84 insertions(+), 84 deletions(-)

Range-diff against v1:
1:  0069b1f385 = 1:  0069b1f385 t/lib-read-tree-m-3way: replace double quotes with single quotes
-:  ---------- > 2:  92e2e6294b t/lib-read-tree-m-3way: replace spaces with tabs
-- 
2.35.0