cmd/go: convert TestLegacyModGet to the script framework

I think this test needs to be split up eventually. It's one of
the longest tests.

Part of converting all tests to script framework to improve
test parallelism.

Updates #36320
Updates #17751

Change-Id: If2168fac040d78fd0ec3dcbdef2affd2a8f48f6d
Reviewed-on: https://go-review.googlesource.com/c/go/+/214158
Reviewed-by: Jay Conrod <jayconrod@google.com>

Author: matloob

src/cmd/go/testdata/script/mod_get_legacy.txt

@@ -0,0 +1,57 @@
+# This test was converted from a test in vendor_test.go (which no longer exists).
+# That seems to imply that it's about vendoring semantics, but the test doesn't
+# use 'go -mod=vendor' (and none of the fetched repos have vendor folders).
+# The test still seems to be useful as a test of direct-mode go get.
+
+[short] skip
+[!exec:git] skip
+
+env GOPATH=$WORK/tmp/d1
+go get vcs-test.golang.org/git/modlegacy1-old.git/p1
+go list -f '{{.Deps}}' vcs-test.golang.org/git/modlegacy1-old.git/p1
+stdout 'new.git/p2' # old/p1 should depend on new/p2
+! stdout new.git/v2/p2 # old/p1 should NOT depend on new/v2/p2
+go build vcs-test.golang.org/git/modlegacy1-old.git/p1 vcs-test.golang.org/git/modlegacy1-new.git/p1
+! stdout .
+
+env GOPATH=$WORK/tmp/d2
+
+rm $GOPATH
+go get github.com/rsc/vgotest5
+go get github.com/rsc/vgotest4
+go get github.com/myitcv/vgo_example_compat
+
+rm $GOPATH
+go get github.com/rsc/vgotest4
+go get github.com/rsc/vgotest5
+go get github.com/myitcv/vgo_example_compat
+
+rm $GOPATH
+go get github.com/rsc/vgotest4 github.com/rsc/vgotest5
+go get github.com/myitcv/vgo_example_compat
+
+rm $GOPATH
+go get github.com/rsc/vgotest5 github.com/rsc/vgotest4
+go get github.com/myitcv/vgo_example_compat
+
+rm $GOPATH
+go get github.com/myitcv/vgo_example_compat
+go get github.com/rsc/vgotest5 github.com/rsc/vgotest4
+
+rm $GOPATH
+go get github.com/myitcv/vgo_example_compat github.com/rsc/vgotest4 github.com/rsc/vgotest5
+
+rm $GOPATH
+go get github.com/myitcv/vgo_example_compat github.com/rsc/vgotest5 github.com/rsc/vgotest4
+
+rm $GOPATH
+go get github.com/rsc/vgotest4 github.com/myitcv/vgo_example_compat github.com/rsc/vgotest5
+
+rm $GOPATH
+go get github.com/rsc/vgotest4 github.com/rsc/vgotest5 github.com/myitcv/vgo_example_compat
+
+rm $GOPATH
+go get github.com/rsc/vgotest5 github.com/myitcv/vgo_example_compat github.com/rsc/vgotest4
+
+rm $GOPATH
+go get github.com/rsc/vgotest5 github.com/rsc/vgotest4 github.com/myitcv/vgo_example_compat