respect --whitelist options when doing a full vendor cycle

Commit b1caa00 added a `--whitelist`
flag to allow ignoring paths in the vendor directory when cleaning up
unused packages/files.

However, 4b11a0f added an optimization
to clean the whole vendor directory when doing a full vendor cycle.
Unfortunately, that change did not take the `--whitelist` option into
account, resulting in whitelisted packages/files to be deleted when doing
a full vendor cycle.

This patch checks if a whitelist option is set when doing a full vendor
cycle, and if so, ignores the specified paths when cleaning.

Using the "v18.06.0-ce" branch on github.com/docker/engine, which has a custom `archive/tar` package in the vendor directory;

    $ git checkout v18.06.0-ce
    $ vndr --whitelist 'archive/tar/.*'
    2020/01/20 18:50:51 Collecting initial packages
    2020/01/20 18:50:52 Download dependencies
    2020/01/20 18:50:55 Starting whole vndr cycle because no package specified
    2020/01/20 18:50:55 Ignoring paths matching "archive/tar/.*"
    ...
    020/01/20 18:53:46  Finished clone github.com/aws/aws-sdk-go
    2020/01/20 18:53:46 Finished clone github.com/hashicorp/consul
    2020/01/20 18:53:46 Dependencies downloaded. Download time: 2m50.469326342s
    2020/01/20 18:53:46 Collecting all dependencies
    2020/01/20 18:53:57 Clean vendor dir from unused packages
    2020/01/20 18:53:57 Ignoring paths matching "archive/tar/.*"
    2020/01/20 18:53:59 Success
    2020/01/20 18:53:59 Running time: 3m7.731082301s

After vendoring completed, verify that the `archive/tar` directory was kept:

    ls vendor/archive/tar
    LICENSE         README.md       common.go       format.go       reader.go       stat_actime1.go stat_actime2.go stat_unix.go    strconv.go      writer.go

Signed-off-by: Sebastiaan van Stijn <github@gone.nl>

main.go

@@ -277,8 +277,17 @@ func main() {
 			cfgDeps = []depEntry{flagDep}
 		} else {
 			log.Println("Starting whole vndr cycle because no package specified")
-			if err := os.RemoveAll(vd); err != nil {
-				log.Fatal(err)
+			if len(cleanWhitelist) > 0 {
+				for _, regex := range cleanWhitelist {
+					log.Printf("\tIgnoring paths matching %q", regex.String())
+				}
+				if err := cleanVendor(vd, nil); err != nil {
+					log.Fatal(err)
+				}
+			} else {
+				if err := os.RemoveAll(vd); err != nil {
+					log.Fatal(err)
+				}
 			}
 		}
 		startDownload := time.Now()

test/vndr_test.go

@@ -314,6 +314,76 @@ github.com/projectatomic/skopeo master`)
 	}
 }
 
+func TestCleanWhitelistFullCycle(t *testing.T) {
+	vndrBin, err := exec.LookPath("vndr")
+	if err != nil {
+		t.Fatal(err)
+	}
+	tmp, err := ioutil.TempDir("", "test-vndr-")
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer os.RemoveAll(tmp)
+	repoDir := filepath.Join(tmp, "src", testRepo)
+	if err := os.MkdirAll(repoDir, 0700); err != nil {
+		t.Fatal(err)
+	}
+	depDir := filepath.Join(repoDir, "vendor", "archive", "tar")
+	if err := os.MkdirAll(depDir, 0700); err != nil {
+		t.Fatal(err)
+	}
+	if err := ioutil.WriteFile(filepath.Join(depDir, "LICENSE"), []byte("foo"), 0644); err != nil {
+		t.Fatal(err)
+	}
+
+	content := []byte(`github.com/AkihiroSuda/dummy-vndr-46 c5613b87bafaaf105fd3857dcae7ef23c931feec
+`)
+	vendorConf := filepath.Join(repoDir, "vendor.conf")
+	if err := ioutil.WriteFile(vendorConf, content, 0666); err != nil {
+		t.Fatal(err)
+	}
+	vndrCmd := exec.Command(vndrBin, "-whitelist", `archive/tar/.*`)
+	vndrCmd.Dir = repoDir
+	setGopath(vndrCmd, tmp)
+
+	out, err := vndrCmd.CombinedOutput()
+	if err != nil {
+		t.Logf("output: %v", string(out))
+		t.Fatalf("error was not expected: %v", err)
+	}
+
+	if !bytes.Contains(out, []byte(fmt.Sprintf(`Ignoring paths matching %q`, `archive/tar/.*`))) {
+		t.Logf("output: %v", string(out))
+		t.Errorf(`output missing regular expression "archive/tar/.*"`)
+	}
+
+	// Make sure that the files were not "cleaned".
+	if _, err := os.Lstat(depDir); err != nil {
+		t.Errorf("%s was cleaned but shouldn't have been", depDir)
+	}
+
+	// Run again to make sure the above will be cleaned.
+	vndrCmd = exec.Command(vndrBin)
+	vndrCmd.Dir = repoDir
+	setGopath(vndrCmd, tmp)
+
+	out, err = vndrCmd.CombinedOutput()
+	if err != nil {
+		t.Logf("output: %v", string(out))
+		t.Fatalf("[no -whitelist] error was not expected: %v", err)
+	}
+
+	if bytes.Contains(out, []byte(fmt.Sprintf(`Ignoring paths matching %q`, `archive/tar/.*`))) {
+		t.Logf("output: %v", string(out))
+		t.Errorf(`[no -whitelist] output should not contain regular expression "archive/tar/.*"`)
+	}
+
+	// Make sure that the files were "cleaned".
+	if _, err := os.Lstat(depDir); err == nil {
+		t.Errorf("[no -whitelist] %s was NOT cleaned but should have been", depDir)
+	}
+}
+
 func TestUnused(t *testing.T) {
 	vndrBin, err := exec.LookPath("vndr")
 	if err != nil {