SCRIPTS: run-regtests: reduce the number of processes needed to check options

run-tegtests is starting to take a lot of time to spot which tests are
eligible, because for each test file a lot of "sed" sub-processes are
launched. This commit eliminates calls to sed by using the shell's
internal processing and parsing the VTC file only once. Instead of
extracting each option one by one from the file, all entries that look
like a valid option are passed to a single case/esac statement and their
value is extracted. Splitting into lists is simply done by adjusting the
IFS depending on the list's delimiter, which, contrary to the // pattern
modifier, is supported on every shell.

This was tested on both bash and dash, and the tests' execution time
dropped by 31% from 8.7 seconds to 6.0 seconds.
1 file changed