Revert "cmd/doc: skip directories like other go tools"

This reverts commit 49e3e436.

Reason for revert: breaks iOS builders and Daniel can't fix for a week.

Change-Id: Ib6ff08de9540d46345dc31e1f820c8555e3de3ca
Reviewed-on: https://go-review.googlesource.com/107218Reviewed-by: Daniel Martí <mvdan@mvdan.cc>
Run-TryBot: Daniel Martí <mvdan@mvdan.cc>
TryBot-Result: Gobot Gobot <gobot@golang.org>

src/cmd/doc/dirs.go

@@ -97,9 +97,8 @@ func (d *Dirs) bfsWalkRoot(root string) {
 					continue
 				}
 				// Entry is a directory.
-
-				// The go tool ignores directories starting with ., _, or named "testdata".
-				if name[0] == '.' || name[0] == '_' || name == "testdata" {
+				// No .git or other dot nonsense please.
+				if strings.HasPrefix(name, ".") {
 					continue
 				}
 				// Remember this (fully qualified) directory for the next pass.

src/cmd/doc/doc_test.go

@@ -16,20 +16,10 @@ import (
 )
 
 func TestMain(m *testing.M) {
-	// Clear GOPATH so we don't access the user's own packages in the test.
+	// otherwise the tests are brittle, as they may give unexpected
+	// output or errors when a suffix match with GOPATH takes place
 	buildCtx.GOPATH = ""
-
 	dirsInit()
-
-	// Add $GOROOT/src/cmd/doc/testdata explicitly so we can access its contents in the test.
-	// Normally testdata directories are ignored, but sending it to dirs.scan directly is
-	// a hack that works around the check.
-	testdataDir, err := filepath.Abs("testdata")
-	if err != nil {
-		panic(err)
-	}
-	go func() { dirs.scan <- testdataDir }()
-
 	os.Exit(m.Run())
 }