t7502-commit.sh: test_must_fail doesn't work with inline environment variables

When the arguments to test_must_fail() begin with a variable assignment, test_must_fail() attempts to execute the variable assignment as a command. This fails, and so test_must_fail returns with a successful status value without running the command it was intended to test. For example, the following script: #!/bin/sh test_must_fail () { "$@" test $? -gt 0 -a $? -le 129 } foo='wo adrian' test_must_fail foo='yo adrian' sh -c 'echo foo: $foo' always exits zero and prints the message: test.sh: line 3: foo=yo adrian: command not found Test 16 calls test_must_fail in such a way and therefore has not been testing whether git 'do[es] not fire editor in the presence of conflicts'. A workaround is to set and export the variable in a normal way, not using one-shot notation. Because this would affect the remainder of the process, the test is done inside a subshell. Signed-off-by: Brandon Casey <casey@nrlssc.navy.mil> Signed-off-by: Junio C Hamano <gitster@pobox.com>