Modernize some testcases for merge-recursive corner cases

I have about a dozen more testcases I want to add to the testsuite, in order to document additional situations that merge-recursive handles suboptimally. To avoid sending an excessively long series, I am splitting this up. This series just aims to modernize a pair of testfiles in which several of the new tests would most naturally belong. This modernization serves two purposes: (1) it makes the existing tests easier to understand, and (2) it simplifies adding more tests to these test files.

Elijah Newren (5):
t6036, t6042: use test_create_repo to keep tests independent t6036, t6042: use test_line_count instead of wc -l
t6036, t6042: prefer test_path_is_file, test_path_is_missing t6036, t6042: prefer test_cmp to sequences of test
t6036: prefer test_when_finished to manual cleanup in following test

 t/t6036-recursive-corner-cases.sh    | 991 +++++++++++++++------------
 t/t6042-merge-rename-corner-cases.sh | 968 ++++++++++++++------------
 2 files changed, 1098 insertions(+), 861 deletions(-)

2.17.0.1.gda85003413