Produce ZIP archives for Windows releases (#195)

On Windows systems tar isn't available by default. This change creates
additional archives in the ZIP format. The tar.gz archive format on
Windows platform is kept for backwards compatibility as some users might
have written custom release scripts assuming this format.

Signed-off-by: Tobias Schmidt <tobidt@gmail.com>

cmd/tarball.go

@@ -15,9 +15,12 @@
 package cmd
 
 import (
+	"archive/zip"
 	"fmt"
+	"io"
 	"os"
 	"path/filepath"
+	"strings"
 
 	"github.com/pkg/errors"
 	kingpin "gopkg.in/alecthomas/kingpin.v2"
@@ -83,4 +86,53 @@ func runTarball(binariesLocation string) {
 	tar := fmt.Sprintf("%s.tar.gz", name)
 	fmt.Println(" >  ", tar)
 	sh.RunCommand("tar", "zcf", filepath.Join(prefix, tar), "-C", tmpDir, name)
+
+	// Windows systems don't have tar available by default. Produce archives in
+	// the common zip format additionally.
+	if goos == "windows" {
+		archive := name + ".zip"
+		fmt.Println(" >  ", archive)
+		if err := createZIP(filepath.Join(prefix, archive), dir); err != nil {
+			fatal(fmt.Errorf("Could not create ZIP archive: %w", err))
+		}
+	}
+}
+
+// createZIP creates a ZIP archive at the given path containing the specified
+// directory.
+func createZIP(path, dir string) error {
+	f, err := os.Create(path)
+	if err != nil {
+		return err
+	}
+	defer f.Close()
+
+	w := zip.NewWriter(f)
+	defer w.Close()
+
+	prefix := filepath.Dir(dir)
+	walker := func(path string, info os.FileInfo, err error) error {
+		if err != nil {
+			return err
+		}
+		if info.IsDir() {
+			return nil
+		}
+
+		r, err := os.Open(path)
+		if err != nil {
+			return err
+		}
+		defer r.Close()
+
+		name := strings.TrimLeft(strings.TrimPrefix(path, prefix), "/")
+		f, err := w.Create(name)
+		if err != nil {
+			return err
+		}
+
+		_, err = io.Copy(f, r)
+		return err
+	}
+	return filepath.Walk(dir, walker)
 }

doc/examples/crossbuild/.promu.yml

@@ -8,6 +8,7 @@ crossbuild:
     platforms:
         - linux/amd64
         - linux/386
+        - windows/amd64
 tarball:
     files:
         - README.md

doc/examples/crossbuild/Makefile

@@ -14,8 +14,13 @@
 # The crossbuild command sets the PREFIX env var for each platform
 PREFIX                  ?= $(shell pwd)
 
+# Workaround to mimic promu's build behavior which usually handles the extension.
+ifeq ($(GOOS),windows)
+	EXTENSION = .exe
+endif
+
 build:
-	go build -o $(PREFIX)/crossbuild-example
+	go build -o $(PREFIX)/crossbuild-example$(EXTENSION)
 
 test:
 	go test

doc/examples/crossbuild/README.md

@@ -1,6 +1,6 @@
 Crossbuild example
 
-Run `promu crossbuild` to crossbuild for linux-386 and linux-amd64 platforms.
+Run `promu crossbuild` to crossbuild for linux-386, linux-amd64, and windows-amd64 platforms.
 Output will be in the `.build` directory.
 
 Run `promu crossbuild tarballs` to build platform tarballs.

main_test.go

@@ -181,6 +181,7 @@ func TestPromuCrossbuild(t *testing.T) {
 	errcheck(t, err, string(output))
 	assertFileExists(t, path.Join(promuExamplesCrossbuild, ".build", "linux-386", "crossbuild-example"))
 	assertFileExists(t, path.Join(promuExamplesCrossbuild, ".build", "linux-amd64", "crossbuild-example"))
+	assertFileExists(t, path.Join(promuExamplesCrossbuild, ".build", "windows-amd64", "crossbuild-example.exe"))
 
 	cmd = exec.Command(promuBinaryAbsPath, "crossbuild", "tarballs")
 	cmd.Dir = promuExamplesCrossbuild
@@ -189,4 +190,6 @@ func TestPromuCrossbuild(t *testing.T) {
 	errcheck(t, err, string(output))
 	assertFileExists(t, path.Join(promuExamplesCrossbuild, ".tarballs", "promu-0.1.linux-386.tar.gz"))
 	assertFileExists(t, path.Join(promuExamplesCrossbuild, ".tarballs", "promu-0.1.linux-amd64.tar.gz"))
+	assertFileExists(t, path.Join(promuExamplesCrossbuild, ".tarballs", "promu-0.1.windows-amd64.tar.gz"))
+	assertFileExists(t, path.Join(promuExamplesCrossbuild, ".tarballs", "promu-0.1.windows-amd64.zip"))
 }