Refactor utils/utils, fixes #11923

Signed-off-by: Antonio Murdaca <me@runcom.ninja>

fileutils/fileutils.go

@@ -1,6 +1,10 @@
 package fileutils
 
 import (
+	"fmt"
+	"io"
+	"io/ioutil"
+	"os"
 	"path/filepath"
 
 	"github.com/Sirupsen/logrus"
@@ -25,3 +29,53 @@ func Matches(relFilePath string, patterns []string) (bool, error) {
 	}
 	return false, nil
 }
+
+func CopyFile(src, dst string) (int64, error) {
+	if src == dst {
+		return 0, nil
+	}
+	sf, err := os.Open(src)
+	if err != nil {
+		return 0, err
+	}
+	defer sf.Close()
+	if err := os.Remove(dst); err != nil && !os.IsNotExist(err) {
+		return 0, err
+	}
+	df, err := os.Create(dst)
+	if err != nil {
+		return 0, err
+	}
+	defer df.Close()
+	return io.Copy(df, sf)
+}
+
+func GetTotalUsedFds() int {
+	if fds, err := ioutil.ReadDir(fmt.Sprintf("/proc/%d/fd", os.Getpid())); err != nil {
+		logrus.Errorf("Error opening /proc/%d/fd: %s", os.Getpid(), err)
+	} else {
+		return len(fds)
+	}
+	return -1
+}
+
+// ReadSymlinkedDirectory returns the target directory of a symlink.
+// The target of the symbolic link may not be a file.
+func ReadSymlinkedDirectory(path string) (string, error) {
+	var realPath string
+	var err error
+	if realPath, err = filepath.Abs(path); err != nil {
+		return "", fmt.Errorf("unable to get absolute path for %s: %s", path, err)
+	}
+	if realPath, err = filepath.EvalSymlinks(realPath); err != nil {
+		return "", fmt.Errorf("failed to canonicalise path for %s: %s", path, err)
+	}
+	realPathInfo, err := os.Stat(realPath)
+	if err != nil {
+		return "", fmt.Errorf("failed to stat target '%s' of '%s': %s", realPath, path, err)
+	}
+	if !realPathInfo.Mode().IsDir() {
+		return "", fmt.Errorf("canonical path points to a file '%s'", realPath)
+	}
+	return realPath, nil
+}