then the go get command has always worked hard to make sure
that it applies the wildcard after downloading rsc/foo.
(If it applied the wildcard only before downloading rsc/foo,
it would match nothing if you had an empty GOPATH before,
and you'd still have an empty afterward, which is clearly useless.)
The goal has always been that if you run the same go get
command twice, the second command doesn't find anything
new to do.
CL 19892 worked around an "internal error" failure but broke
the rule about the first command doing everything the second
command would. Suppose you had github.com/rsc/foo already,
with just github.com/rsc/foo/bar, and you run
go get -u github.com/rsc/...
The wildcard first matches github.com/rsc/foo/bar, but suppose
updating the repo pulls down github.com/rsc/foo/baz, which
in turn depends on the non-existent package github.com/rsc/quux.
We need to reevaluate the wildcard after the download.
The new pattern match refactoring makes this easier and happened
to have corrected the behavior, but we missed a long test that
expected the old behavior.