builder: modernize TestCheckoutGit

Make the test more debuggable by logging all git command output and
running each table-driven test case as a subtest.

Signed-off-by: Cory Snider <csnider@mirantis.com>

builder/remotecontext/git/gitutils_test.go

@@ -2,7 +2,6 @@ package git // import "github.com/docker/docker/builder/remotecontext/git"
 
 import (
 	"fmt"
-	"io/ioutil"
 	"net/http"
 	"net/http/httptest"
 	"net/url"
@@ -171,9 +170,7 @@ func gitGetConfig(name string) string {
 }
 
 func TestCheckoutGit(t *testing.T) {
-	root, err := ioutil.TempDir("", "docker-build-git-checkout")
+	root := t.TempDir()
-	assert.NilError(t, err)
-	defer os.RemoveAll(root)
 
 	autocrlf := gitGetConfig("core.autocrlf")
 	if !(autocrlf == "true" || autocrlf == "false" ||
@@ -185,88 +182,57 @@ func TestCheckoutGit(t *testing.T) {
 		eol = "\r\n"
 	}
 
+	must := func(out []byte, err error) {
+		t.Helper()
+		if len(out) > 0 {
+			t.Logf("%s", out)
+		}
+		assert.NilError(t, err)
+	}
+
 	gitDir := filepath.Join(root, "repo")
-	_, err = git("init", gitDir)
+	must(git("-c", "init.defaultBranch=master", "init", gitDir))
-	assert.NilError(t, err)
+	must(gitWithinDir(gitDir, "config", "user.email", "test@docker.com"))
-
+	must(gitWithinDir(gitDir, "config", "user.name", "Docker test"))
-	_, err = gitWithinDir(gitDir, "config", "user.email", "test@docker.com")
+	assert.NilError(t, os.WriteFile(filepath.Join(gitDir, "Dockerfile"), []byte("FROM scratch"), 0644))
-	assert.NilError(t, err)
-
-	_, err = gitWithinDir(gitDir, "config", "user.name", "Docker test")
-	assert.NilError(t, err)
-
-	err = ioutil.WriteFile(filepath.Join(gitDir, "Dockerfile"), []byte("FROM scratch"), 0644)
-	assert.NilError(t, err)
 
 	subDir := filepath.Join(gitDir, "subdir")
 	assert.NilError(t, os.Mkdir(subDir, 0755))
-
+	assert.NilError(t, os.WriteFile(filepath.Join(subDir, "Dockerfile"), []byte("FROM scratch\nEXPOSE 5000"), 0644))
-	err = ioutil.WriteFile(filepath.Join(subDir, "Dockerfile"), []byte("FROM scratch\nEXPOSE 5000"), 0644)
-	assert.NilError(t, err)
 
 	if runtime.GOOS != "windows" {
-		if err = os.Symlink("../subdir", filepath.Join(gitDir, "parentlink")); err != nil {
+		assert.NilError(t, os.Symlink("../subdir", filepath.Join(gitDir, "parentlink")))
-			t.Fatal(err)
+		assert.NilError(t, os.Symlink("/subdir", filepath.Join(gitDir, "absolutelink")))
 	}
 
-		if err = os.Symlink("/subdir", filepath.Join(gitDir, "absolutelink")); err != nil {
+	must(gitWithinDir(gitDir, "add", "-A"))
-			t.Fatal(err)
+	must(gitWithinDir(gitDir, "commit", "-am", "First commit"))
-		}
+	must(gitWithinDir(gitDir, "checkout", "-b", "test"))
-	}
 
-	_, err = gitWithinDir(gitDir, "add", "-A")
+	assert.NilError(t, os.WriteFile(filepath.Join(gitDir, "Dockerfile"), []byte("FROM scratch\nEXPOSE 3000"), 0644))
-	assert.NilError(t, err)
+	assert.NilError(t, os.WriteFile(filepath.Join(subDir, "Dockerfile"), []byte("FROM busybox\nEXPOSE 5000"), 0644))
 
-	_, err = gitWithinDir(gitDir, "commit", "-am", "First commit")
+	must(gitWithinDir(gitDir, "add", "-A"))
-	assert.NilError(t, err)
+	must(gitWithinDir(gitDir, "commit", "-am", "Branch commit"))
-
+	must(gitWithinDir(gitDir, "checkout", "master"))
-	_, err = gitWithinDir(gitDir, "checkout", "-b", "test")
-	assert.NilError(t, err)
-
-	err = ioutil.WriteFile(filepath.Join(gitDir, "Dockerfile"), []byte("FROM scratch\nEXPOSE 3000"), 0644)
-	assert.NilError(t, err)
-
-	err = ioutil.WriteFile(filepath.Join(subDir, "Dockerfile"), []byte("FROM busybox\nEXPOSE 5000"), 0644)
-	assert.NilError(t, err)
-
-	_, err = gitWithinDir(gitDir, "add", "-A")
-	assert.NilError(t, err)
-
-	_, err = gitWithinDir(gitDir, "commit", "-am", "Branch commit")
-	assert.NilError(t, err)
-
-	_, err = gitWithinDir(gitDir, "checkout", "master")
-	assert.NilError(t, err)
 
 	// set up submodule
 	subrepoDir := filepath.Join(root, "subrepo")
-	_, err = git("init", subrepoDir)
+	must(git("-c", "init.defaultBranch=master", "init", subrepoDir))
-	assert.NilError(t, err)
+	must(gitWithinDir(subrepoDir, "config", "user.email", "test@docker.com"))
+	must(gitWithinDir(subrepoDir, "config", "user.name", "Docker test"))
 
-	_, err = gitWithinDir(subrepoDir, "config", "user.email", "test@docker.com")
+	assert.NilError(t, os.WriteFile(filepath.Join(subrepoDir, "subfile"), []byte("subcontents"), 0644))
-	assert.NilError(t, err)
 
-	_, err = gitWithinDir(subrepoDir, "config", "user.name", "Docker test")
+	must(gitWithinDir(subrepoDir, "add", "-A"))
-	assert.NilError(t, err)
+	must(gitWithinDir(subrepoDir, "commit", "-am", "Subrepo initial"))
-
-	err = ioutil.WriteFile(filepath.Join(subrepoDir, "subfile"), []byte("subcontents"), 0644)
-	assert.NilError(t, err)
-
-	_, err = gitWithinDir(subrepoDir, "add", "-A")
-	assert.NilError(t, err)
-
-	_, err = gitWithinDir(subrepoDir, "commit", "-am", "Subrepo initial")
-	assert.NilError(t, err)
 
 	cmd := exec.Command("git", "submodule", "add", subrepoDir, "sub") // this command doesn't work with --work-tree
 	cmd.Dir = gitDir
-	assert.NilError(t, cmd.Run())
+	must(cmd.CombinedOutput())
 
-	_, err = gitWithinDir(gitDir, "add", "-A")
+	must(gitWithinDir(gitDir, "add", "-A"))
-	assert.NilError(t, err)
+	must(gitWithinDir(gitDir, "commit", "-am", "With submodule"))
-
-	_, err = gitWithinDir(gitDir, "commit", "-am", "With submodule")
-	assert.NilError(t, err)
 
 	type singleCase struct {
 		frag      string
@@ -300,17 +266,18 @@ func TestCheckoutGit(t *testing.T) {
 	}
 
 	for _, c := range cases {
+		t.Run(c.frag, func(t *testing.T) {
 			ref, subdir := getRefAndSubdir(c.frag)
 			r, err := cloneGitRepo(gitRepo{remote: gitDir, ref: ref, subdir: subdir})
 
 			if c.fail {
 				assert.Check(t, is.ErrorContains(err, ""))
-			continue
+				return
 			}
 			assert.NilError(t, err)
 			defer os.RemoveAll(r)
 			if c.submodule {
-			b, err := ioutil.ReadFile(filepath.Join(r, "sub/subfile"))
+				b, err := os.ReadFile(filepath.Join(r, "sub/subfile"))
 				assert.NilError(t, err)
 				assert.Check(t, is.Equal("subcontents", string(b)))
 			} else {
@@ -319,9 +286,10 @@ func TestCheckoutGit(t *testing.T) {
 				assert.Assert(t, os.IsNotExist(err))
 			}
 
-		b, err := ioutil.ReadFile(filepath.Join(r, "Dockerfile"))
+			b, err := os.ReadFile(filepath.Join(r, "Dockerfile"))
 			assert.NilError(t, err)
 			assert.Check(t, is.Equal(c.exp, string(b)))
+		})
 	}
 }