Before adding any more features to todo_completion, I feel like I need test coverage, so this is a first stab at testing the completion results, via a new test function test_todo_completion.
Some basic tests showcase the capabilities.
Note: test-lib.sh now uses arrays, therefore all tests must use /bin/bash, not /bin/sh to avoid errors when sourcing test-lib. For consistency with todo.sh, we should have used Bash everywhere, anyway. Also note that t2000-multiline.sh needs some more quoting to avoid "Bash: ambiguous redirect" errors.
* Fix sed error on Mac OS, also ignore entire commented lines.
* With proper quoting, the non-POSIX \d96 escape isn't necessary, and the check should work also on Mac OS.
Pull request #26 by trajano (e24777fa2c) changed `...` to $(...), but the following commit 7900ad7e1b already added another old-style one. I think the tests can also be used for some simple enforcement of coding style, so here is a first shot at it.
Closes#46
