cmd/go: use tags when evaluating file system wildcards like ./...

Thanks to Albert Hafvenström for the diagnosis.

Fixes #11246.

Change-Id: I2b9e670c0ecf6aa01e5bf4d7a402619e93cc4f4a
Reviewed-on: https://go-review.googlesource.com/17942Reviewed-by: Ian Lance Taylor <iant@golang.org>

src/cmd/go/go_test.go

@@ -781,6 +781,16 @@ func TestGoInstallDetectsRemovedFiles(t *testing.T) {
 	tg.wantStale("mypkg", "./testgo list mypkg claims mypkg is NOT stale after removing y.go; should be stale")
 }
 
+func TestGoListWithTags(t *testing.T) {
+	tg := testgo(t)
+	defer tg.cleanup()
+	tg.tempFile("src/mypkg/x.go", "// +build thetag\n\npackage mypkg\n")
+	tg.setenv("GOPATH", tg.path("."))
+	tg.cd(tg.path("./src"))
+	tg.run("list", "-tags=thetag", "./my...")
+	tg.grepStdout("mypkg", "did not find mypkg")
+}
+
 func TestGoInstallErrorOnCrossCompileToBin(t *testing.T) {
 	if testing.Short() {
 		t.Skip("don't install into GOROOT in short mode")

src/cmd/go/main.go

@@ -674,7 +674,7 @@ func matchPackagesInFS(pattern string) []string {
 		if !match(name) {
 			return nil
 		}
-		if _, err = build.ImportDir(path, 0); err != nil {
+		if _, err = buildContext.ImportDir(path, 0); err != nil {
 			if _, noGo := err.(*build.NoGoError); !noGo {
 				log.Print(err)
 			}