test-tool run-command testsuite: get shell from env
When running tests through `test-tool run-command testsuite`, we currently hardcode `sh` as the command interpreter. As discussed in [1], this is incorrect, and we should be using the shell set in TEST_SHELL_PATH instead. Add a shell_path field in struct testsuite so that we can pass this to the task runner callback. If this is non-null, we'll use it as the argv[0] of the subprocess. Otherwise, we'll just execute the test program directly. We will use this feature in a later commit to enable running binary executable unit tests. However, for now when setting up the struct testsuite in testsuite(), use the value of TEST_SHELL_PATH if it's set, otherwise keep the original behavior by defaulting to `sh`. [1] https://lore.kernel.org/git/20240123005913.GB835964@coredump.intra.peff.net/ Signed-off-by: Josh Steadmon <steadmon@google.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>