For backwards compatibility reasons, we transform some wildmatch
patterns. However, when we're reading a pattern from .gitattributes, we
do this as well, and these transformations can cause us to fail to match
some things that Git does match.
While we want to retain the behavior of the command-line options for
compatibility, at least until 3.0, there's no reason for us to mismatch
patterns in .gitattributes: that's clearly a bug. Let's add an option
to our pattern constructor to match patterns strictly so we can enable
it when reading from .gitattributes, and disable our pattern
manipulation when it's enabled.
To help us improve debugging, let's also add the value of the strictness
flag when printing the transformed pattern.
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