This commit also forbids composing lvalues of composed matchers, as
per previous deprecation notice. I do not expect this to be contentious
in practice, because there was a bug in that usage for years, and
nobody complained.
Given that in the 2 or so years that matchers are thing nobody complained,
it seems that people do not actually write this sort of code, and the
possibility will be removed in v3. However, to avoid correctness bugs,
we will have to support this weird code in v2.
This also required some refactoring of how the pattern matching
works. This means that the concepts of include and exclude patterns
are no longer unified, with exclusion patterns working as just
negation of an inclusion patterns (which led to including hidden
tags by default, as they did not match the exclusion), but rather
both include and exclude patterns are handled separately.
The new logic is that given a filter and a test case, the test
case must match _all_ include patterns and _no_ exclude patterns
to be included by the filter. Furthermore, if the test case is
hidden, then the filter must have at least one include pattern
for the test case to be used.
Closes#1184
This captures the intent better, as some changes are indeed plain
deprecations leading to removal, but other changes can be viewed
as minor tune-ups instead.
