test-lib: avoid accidental globbing in match_pattern_list()

We have a custom match_pattern_list() function which we use for matching test names (like "t1234") against glob-like patterns (like "t1???") for $GIT_SKIP_TESTS, --verbose-only, etc. Those patterns may have multiple whitespace-separated elements (e.g., "t0* t1234 t5?78"). The callers of match_pattern_list thus pass the strings unquoted, so that the shell does the usual field-splitting into separate arguments. But this also means the shell will do the usual globbing for each argument, which can result in us seeing an expansion based on what's in the filesystem, rather than the real pattern. For example, if I have the path "t5000" in the filesystem, and you feed the pattern "t?000", that _should_ match the string "t0000", but it won't after the shell has expanded it to "t5000". This has been a bug ever since that function was introduced. But it didn't usually trigger since we typically use the function inside the trash directory, which has a very limited set of files that are unlikely to match. It became a lot easier to trigger after edc23840b0 (test-lib: bring $remove_trash out of retirement, 2021-05-10), because now we match $GIT_SKIP_TESTS before even entering the trash directory. So the t5000 example above can be seen with: GIT_SKIP_TESTS=t?000 ./t0000-basic.sh which should skip all tests but doesn't. We can fix this by using "set -f" to ask the shell not to glob (which is in POSIX, so should hopefully be portable enough). We only want to do this in a subshell (to avoid polluting the rest of the script), which means we need to get the whole string intact into the match_pattern_list function by quoting it. Arguably this is a good idea anyway, since it makes it much more obvious that we intend to split, and it's not simply sloppy scripting. Diagnosed-by: Junio C Hamano <gitster@pobox.com> Signed-off-by: Jeff King <peff@peff.net> Signed-off-by: Junio C Hamano <gitster@pobox.com>