Add some golang file manipulation utility functions

Some dead-simple file manipulation functions.

tools/file/file.go

@@ -0,0 +1,31 @@
+package file
+
+import (
+	"io"
+	"os"
+	"path/filepath"
+	"runtime"
+
+	"github.com/attic-labs/noms/d"
+)
+
+// DumbCopy copies the contents of a regular file at srcPath (following symlinks) to a new regular file at dstPath. New file is created with mode 0644.
+func DumbCopy(srcPath, dstPath string) {
+	chkClose := func(c io.Closer) { d.Exp.NoError(c.Close()) }
+	src, err := os.Open(srcPath)
+	d.Exp.NoError(err)
+	defer chkClose(src)
+
+	dst, err := os.OpenFile(dstPath, os.O_WRONLY|os.O_CREATE|os.O_TRUNC, 0644)
+	d.Exp.NoError(err)
+	defer chkClose(dst)
+	_, err = io.Copy(dst, src)
+	d.Exp.NoError(err)
+}
+
+// MyDir returns the directory in which the file containing the calling source code resides.
+func MyDir() string {
+	_, path, _, ok := runtime.Caller(0)
+	d.Chk.True(ok, "Should have been able to get Caller.")
+	return filepath.Dir(path)
+}

tools/file/file_test.go

@@ -0,0 +1,69 @@
+package file
+
+import (
+	"io/ioutil"
+	"os"
+	"path/filepath"
+	"testing"
+
+	"github.com/attic-labs/noms/Godeps/_workspace/src/github.com/stretchr/testify/suite"
+	"github.com/attic-labs/noms/d"
+)
+
+const (
+	contents = "hey"
+)
+
+func TestSerialRunnerTestSuite(t *testing.T) {
+	suite.Run(t, &FileTestSuite{})
+}
+
+type FileTestSuite struct {
+	suite.Suite
+	dir, src string
+}
+
+func (suite *FileTestSuite) SetupTest() {
+	var err error
+	suite.dir, err = ioutil.TempDir(os.TempDir(), "")
+	suite.NoError(err)
+	suite.src = filepath.Join(suite.dir, "srcfile")
+	suite.NoError(ioutil.WriteFile(suite.src, []byte(contents), 0644))
+}
+
+func (suite *FileTestSuite) TearDownTest() {
+	os.Remove(suite.dir)
+}
+
+func (suite *FileTestSuite) TestCopyFile() {
+	dst := filepath.Join(suite.dir, "dstfile")
+	suite.NoError(d.Try(func() { DumbCopy(suite.src, dst) }))
+
+	out, err := ioutil.ReadFile(dst)
+	suite.NoError(err)
+	suite.Equal(contents, string(out))
+}
+
+func (suite *FileTestSuite) TestCopyLink() {
+	link := filepath.Join(suite.dir, "link")
+	suite.NoError(os.Symlink(suite.src, link))
+
+	dst := filepath.Join(suite.dir, "dstfile")
+	suite.NoError(d.Try(func() { DumbCopy(link, dst) }))
+
+	info, err := os.Lstat(dst)
+	suite.NoError(err)
+	suite.True(info.Mode().IsRegular())
+
+	out, err := ioutil.ReadFile(dst)
+	suite.NoError(err)
+	suite.Equal(contents, string(out))
+}
+
+func (suite *FileTestSuite) TestNoCopyDir() {
+	dir, err := ioutil.TempDir(suite.dir, "")
+	suite.NoError(err)
+
+	dst := filepath.Join(suite.dir, "dst")
+	suite.Error(d.Try(func() { DumbCopy(dir, dst) }))
+}