t7600: use test_config to set/unset git config variables

Instead of using construct such as:
    test_when_finished "git config --unset <key>"
    git config <key> <value>
uses
    test_config <key> <value>
The latter takes care of removing <key> at the end of the test.

Tests are modified to assume default configuration at entry,
and to reset the modified configuration variables at the end.

Test 'merge log message' was relying on the presence of option `--no-ff`
in the configuration. With the option, git show -s --pretty=format:%b HEAD
produces an empty line and without the option, it produces an empty file.
The test is modified to check with and without `--no-ff` option.

Signed-off-by: Yann Droneaud <ydroneaud@opteya.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

0 files changed, 0 insertions, 0 deletions