cmd/go: ignore custom import check when there is no import comment

Fixes #10952

Change-Id: I56ab6a806bd3741cffd9d2a53929a6d043626a26
Reviewed-on: https://go-review.googlesource.com/10693Reviewed-by: Russ Cox <rsc@golang.org>

src/cmd/go/get.go

@@ -314,7 +314,7 @@ func downloadPackage(p *Package) error {
 							repo = resolved
 						}
 					}
-					if remote != repo {
+					if remote != repo && p.ImportComment != "" {
 						return fmt.Errorf("%s is a custom import path for %s, but %s is checked out from %s", rr.root, repo, dir, remote)
 					}
 				}

src/cmd/go/go_test.go

@@ -278,6 +278,30 @@ func (tg *testgoData) runFail(args ...string) {
 	}
 }
 
+// runGit runs a git command, and expects it to succeed.
+func (tg *testgoData) runGit(dir string, args ...string) {
+	cmd := exec.Command("git", args...)
+	tg.stdout.Reset()
+	tg.stderr.Reset()
+	cmd.Stdout = &tg.stdout
+	cmd.Stderr = &tg.stderr
+	cmd.Dir = dir
+	cmd.Env = tg.env
+	status := cmd.Run()
+	if tg.stdout.Len() > 0 {
+		tg.t.Log("git standard output:")
+		tg.t.Log(tg.stdout.String())
+	}
+	if tg.stderr.Len() > 0 {
+		tg.t.Log("git standard error:")
+		tg.t.Log(tg.stderr.String())
+	}
+	if status != nil {
+		tg.t.Logf("git %v failed unexpectedly: %v", args, status)
+		tg.t.FailNow()
+	}
+}
+
 // getStdout returns standard output of the testgo run as a string.
 func (tg *testgoData) getStdout() string {
 	if !tg.ran {
@@ -932,6 +956,24 @@ func TestImportCommentConflict(t *testing.T) {
 	tg.grepStderr("found import comments", "go build did not mention comment conflict")
 }
 
+// cmd/go: custom import path checking should not apply to github.com/xxx/yyy.
+func TestIssue10952(t *testing.T) {
+	if _, err := exec.LookPath("git"); err != nil {
+		t.Skip("skipping because git binary not found")
+	}
+
+	tg := testgo(t)
+	defer tg.cleanup()
+	tg.parallel()
+	tg.tempDir("src")
+	tg.setenv("GOPATH", tg.path("."))
+	const importPath = "github.com/zombiezen/go-get-issue-10952"
+	tg.run("get", "-d", "-u", importPath)
+	repoDir := tg.path("src/" + importPath)
+	tg.runGit(repoDir, "remote", "set-url", "origin", "https://"+importPath+".git")
+	tg.run("get", "-d", "-u", importPath)
+}
+
 func TestDisallowedCSourceFiles(t *testing.T) {
 	tg := testgo(t)
 	defer tg.cleanup()