feat(gerrit): Create detzip, a small helper utility for packing zips determinstically. r/946

detzip will be used in a patch for the Gerrit bower repository helper, which allows
us to get consistent hashes for the output of fetching the dependencies for the
Bazel build.

Change-Id: I6c87b19815b9d747064108aecbb57ed875d2623b
Reviewed-on: https://cl.tvl.fyi/c/depot/+/251
Reviewed-by: lukegb <lukegb@tvl.fyi>

1 files changed, 97 insertions, 0 deletions

diff --git a/third_party/gerrit/detzip.go b/third_party/gerrit/detzip.go
new file mode 100644
index 0000000000..511c18ecfe
--- /dev/null
+++ b/third_party/gerrit/detzip.go
@@ -0,0 +1,97 @@
+package main
+
+import (
+	"archive/zip"
+	"flag"
+	"fmt"
+	"io"
+	"log"
+	"os"
+	"path/filepath"
+	"sort"
+	"strings"
+)
+
+var (
+	exclude = flag.String("exclude", "", "comma-separated list of filenames to exclude (in any directory)")
+)
+
+func init() {
+	flag.Usage = func() {
+		fmt.Fprintf(flag.CommandLine.Output(), "Usage of %s [zip file] [directory]:\n", os.Args[0])
+		flag.PrintDefaults()
+	}
+}
+
+func listToMap(ss []string) map[string]bool {
+	m := make(map[string]bool)
+	for _, s := range ss {
+		m[s] = true
+	}
+	return m
+}
+
+func main() {
+	flag.Parse()
+	if flag.NArg() != 2 {
+		flag.Usage()
+		os.Exit(1)
+	}
+
+	outPath := flag.Arg(0)
+	dirPath := flag.Arg(1)
+
+	excludeFiles := listToMap(strings.Split(*exclude, ","))
+
+	// Aggregate all files first.
+	var files []string
+	filepath.Walk(dirPath, func(path string, info os.FileInfo, err error) error {
+		if err != nil {
+			return err
+		}
+		if info.IsDir() {
+			return nil
+		}
+		if excludeFiles[info.Name()] {
+			return nil
+		}
+		files = append(files, path)
+		return nil
+	})
+
+	// Create zip
+	outW, err := os.Create(outPath)
+	if err != nil {
+		log.Fatalf("Create(%q): %v", outPath, err)
+	}
+
+	zipW := zip.NewWriter(outW)
+
+	// Output files in alphabetical order
+	sort.Strings(files)
+	for _, f := range files {
+		fw, err := zipW.CreateHeader(&zip.FileHeader{
+			Name:   f,
+			Method: zip.Store,
+		})
+		if err != nil {
+			log.Fatalf("creating %q in zip: %v", f, err)
+		}
+
+		ff, err := os.Open(f)
+		if err != nil {
+			log.Fatalf("opening %q: %v", f, err)
+		}
+		if _, err := io.Copy(fw, ff); err != nil {
+			log.Fatalf("copying %q to zip: %v", f, err)
+		}
+		ff.Close()
+	}
+
+	if err := zipW.Close(); err != nil {
+		log.Fatalf("writing ZIP central directory: %v", err)
+	}
+	if err := outW.Close(); err != nil {
+		log.Fatalf("closing ZIP file: %v", err)
+	}
+}