cmd/gitmirror: directly specify local paths for testing

Currently tests `insteadOf` options in the global git configuration to
redirect the upsteam paths that gitMirror is trying to use. Make this
more straightforward by directly configuring the local paths.

The biggest change here is to change the upstream base URL, goBase, to a
field in the gitMirror struct.

For golang/go#60877.

Change-Id: I1a0a95d3b7fb44d60639177a8579a61631714f81
Reviewed-on: https://go-review.googlesource.com/c/build/+/504675
TryBot-Result: Gopher Robot <gobot@golang.org>
Run-TryBot: Michael Pratt <mpratt@google.com>
Auto-Submit: Michael Pratt <mpratt@google.com>
Reviewed-by: Heschi Kreinick <heschi@google.com>

cmd/gitmirror/gitmirror.go

@@ -37,10 +37,6 @@ import (
 	"golang.org/x/sync/errgroup"
 )
 
-const (
-	goBase = "https://go.googlesource.com/"
-)
-
 var (
 	flagHTTPAddr     = flag.String("http", "", "If non-empty, the listen address to run an HTTP server on")
 	flagCacheDir     = flag.String("cachedir", "", "git cache directory. If empty a temp directory is made.")
@@ -82,6 +78,7 @@ func main() {
 		repos:        map[string]*repo{},
 		cacheDir:     cacheDir,
 		homeDir:      credsDir,
+		goBase:       "https://go.googlesource.com/",
 		gerritClient: gerrit.NewClient("https://go-review.googlesource.com", gerrit.NoAuth),
 		mirrorGitHub: *flagMirrorGitHub,
 		mirrorCSR:    *flagMirrorCSR,
@@ -203,6 +200,7 @@ type gitMirror struct {
 	cacheDir string
 	// homeDir is used as $HOME for all commands, allowing easy configuration overrides.
 	homeDir                 string
+	goBase                  string // Base URL/path for Go upstream repos.
 	gerritClient            *gerrit.Client
 	mirrorGitHub, mirrorCSR bool
 	timeoutScale            int
@@ -212,7 +210,7 @@ func (m *gitMirror) addRepo(meta *repospkg.Repo) *repo {
 	name := meta.GoGerritProject
 	r := &repo{
 		name:    name,
-		url:     goBase + name,
+		url:     m.goBase + name,
 		meta:    meta,
 		root:    filepath.Join(m.cacheDir, name),
 		changed: make(chan bool, 1),

cmd/gitmirror/gitmirror_test.go

@@ -5,7 +5,6 @@
 package main
 
 import (
-	"bytes"
 	"fmt"
 	"io/ioutil"
 	"net/http"
@@ -96,6 +95,7 @@ func TestMirrorInitiallyEmpty(t *testing.T) {
 }
 
 type testMirror struct {
+	// Local paths to the copies of the build repo.
 	gerrit, github, csr string
 	m                   *gitMirror
 	server              *httptest.Server
@@ -112,14 +112,26 @@ func newTestMirror(t *testing.T) *testMirror {
 		t.Skip("skipping; git not in PATH")
 	}
 
+	goBase := t.TempDir()
+	gerrit := filepath.Join(goBase, "build")
+	if err := os.Mkdir(gerrit, 0755); err != nil {
+		t.Fatalf("error creating gerrit build directory: %v", err)
+	}
+
 	tm := &testMirror{
-		gerrit: t.TempDir(),
+		gerrit: gerrit,
 		github: t.TempDir(),
 		csr:    t.TempDir(),
 		m: &gitMirror{
-			mux:          http.NewServeMux(),
-			cacheDir:     t.TempDir(),
-			homeDir:      t.TempDir(),
+			mux:      http.NewServeMux(),
+			cacheDir: t.TempDir(),
+			homeDir:  t.TempDir(),
+			// gitMirror generally expects goBase to be a URL, not
+			// a path, but git handles local paths just fine. As a
+			// result, gitMirror uses standard string concatenation
+			// rather than path.Join. Ensure the path ends in / to
+			// make sure concatenation is OK.
+			goBase:       goBase + "/",
 			repos:        map[string]*repo{},
 			mirrorGitHub: true,
 			mirrorCSR:    true,
@@ -131,11 +143,9 @@ func newTestMirror(t *testing.T) *testMirror {
 	tm.server = httptest.NewServer(tm.m.mux)
 	t.Cleanup(tm.server.Close)
 
-	// Write a git config with each of the relevant repositories replaced by a
-	// local version. The origin is non-bare so we can commit to it; the
-	// destinations are bare so we can push to them.
-	gitConfig := &bytes.Buffer{}
-	overrideRepo := func(fromURL, toDir string, bare bool) {
+	// The origin is non-bare so we can commit to it; the destinations are
+	// bare so we can push to them.
+	initRepo := func(dir string, bare bool) {
 		initArgs := []string{"init"}
 		if bare {
 			initArgs = append(initArgs, "--bare")
@@ -146,24 +156,16 @@ func newTestMirror(t *testing.T) *testMirror {
 			{"config", "user.email", "gopher@golang.org"},
 		} {
 			cmd := exec.Command("git", args...)
-			envutil.SetDir(cmd, toDir)
+			envutil.SetDir(cmd, dir)
 			if out, err := cmd.CombinedOutput(); err != nil {
 				t.Fatalf("%s: %v\n%s", strings.Join(cmd.Args, " "), err, out)
 			}
 		}
+	}
+	initRepo(tm.gerrit, false)
+	initRepo(tm.github, true)
+	initRepo(tm.csr, true)
 
-		fmt.Fprintf(gitConfig, "[url %q]\n  insteadOf = %v\n", toDir, fromURL)
-	}
-	overrideRepo("https://go.googlesource.com/build", tm.gerrit, false)
-	overrideRepo("git@github.com:golang/build.git", tm.github, true)
-	overrideRepo("https://source.developers.google.com/p/golang-org/r/build", tm.csr, true)
-
-	if err := os.MkdirAll(filepath.Join(tm.m.homeDir, ".config/git"), 0777); err != nil {
-		t.Fatal(err)
-	}
-	if err := ioutil.WriteFile(filepath.Join(tm.m.homeDir, ".config/git/config"), gitConfig.Bytes(), 0777); err != nil {
-		t.Fatal(err)
-	}
 	tm.buildRepo = tm.m.addRepo(&repospkg.Repo{
 		GoGerritProject:    "build",
 		ImportPath:         "golang.org/x/build",
@@ -174,9 +176,13 @@ func newTestMirror(t *testing.T) *testMirror {
 	if err := tm.buildRepo.init(); err != nil {
 		t.Fatal(err)
 	}
-	if err := tm.m.addMirrors(); err != nil {
-		t.Fatal(err)
-	}
+
+	// Manually add mirror repos. We can't use tm.m.addMirrors, as they
+	// hard-codes the real remotes, but we need to use local test
+	// directories.
+	tm.buildRepo.addRemote("github", tm.github)
+	tm.buildRepo.addRemote("csr", tm.csr)
+
 	return tm
 }