tools: wrap os.Getwd with cygwin support

tools/cygwin.go

@@ -0,0 +1,7 @@
+// +build !windows
+
+package tools
+
+func isCygwin() bool {
+	return false
+}

tools/cygwin_windows.go

@@ -0,0 +1,18 @@
+// +build windows
+
+package tools
+
+import (
+	"bytes"
+
+	"github.com/git-lfs/git-lfs/subprocess"
+)
+
+func isCygwin() bool {
+	cmd := subprocess.ExecCommand("uname")
+	out, err := cmd.Output()
+	if err != nil {
+		return false
+	}
+	return bytes.Contains(out, []byte("CYGWIN"))
+}

tools/os_tools.go

@@ -0,0 +1,51 @@
+package tools
+
+import (
+	"bytes"
+	"fmt"
+	"os"
+	"strings"
+
+	"github.com/git-lfs/git-lfs/subprocess"
+	"github.com/pkg/errors"
+)
+
+func Getwd() (dir string, err error) {
+	dir, err = os.Getwd()
+	if err != nil {
+		return
+	}
+
+	if isCygwin() {
+		dir, err = translateCygwinPath(dir)
+		if err != nil {
+			return "", errors.Wrap(err, "convert wd to cygwin")
+		}
+	}
+
+	return
+}
+
+func translateCygwinPath(path string) (string, error) {
+	cmd := subprocess.ExecCommand("cygpath", "-w", path)
+	buf := &bytes.Buffer{}
+	cmd.Stderr = buf
+	out, err := cmd.Output()
+	output := strings.TrimSpace(string(out))
+	if err != nil {
+		return path, fmt.Errorf("Failed to translate path from cygwin to windows: %s", buf.String())
+	}
+	return output, nil
+}
+
+func TranslateIfCygwin(path string) (string, error) {
+	if isCygwin() {
+		var err error
+
+		path, err = translateCygwinPath(path)
+		if err != nil {
+			return "", err
+		}
+	}
+	return path, nil
+}