feat: implement following symlinks

This feature lets us replace symlinks to files with the actual files they point to. Symlinks to directories are NOT walked. Symlinks to non-regular files will remain symlinks.

archiver/archive.go

@@ -108,23 +108,36 @@ func writeZip(archiveFile *os.File, filesToBackup []BackupFileMetadata) {
 }
 
 func addFileToTar(tw *tar.Writer, path string, pathInArchive string) error {
-	file, err := os.Open(path)
-	if err != nil {
-		return err
-	}
-	defer file.Close()
-
 	if stat, err := os.Lstat(path); err == nil {
 		var linkTarget string
 		// Check if file is symlink
 		if stat.Mode()&os.ModeSymlink != 0 {
-			log.Printf("Found link: %s", path)
 			var err error
 			linkTarget, err = os.Readlink(path)
 			if err != nil {
 				return fmt.Errorf("%s: readlink: %v", stat.Name(), err)
 			}
+
+			// In case the user wants to follow symlinks we eval the symlink target
+			if currentUnitConfig.FollowSymlinks {
+				if linkTargetPath, err := filepath.EvalSymlinks(path); err == nil {
+					if linkTargetInfo, statErr := os.Stat(linkTargetPath); statErr == nil {
+						if linkTargetInfo.Mode().IsRegular() {
+							// If file is regular, we can simply replace the symlink with the actual file
+							path = linkTargetPath
+							linkTarget = ""
+							stat = linkTargetInfo
+						}
+					}
+				}
+			}
+		}
+
+		file, err := os.Open(path)
+		if err != nil {
+			return err
 		}
+		defer file.Close()
 
 		// now lets create the header as needed for this file within the tarball
 		header, err := tar.FileInfoHeader(stat, filepath.ToSlash(linkTarget))

config/config.go

@@ -17,6 +17,7 @@ type Unit struct {
 	AddSubfolder     bool
 	Enabled          bool
 	UseAbsolutePaths bool
+	FollowSymlinks   bool
 }
 
 type Config struct {
@@ -32,6 +33,7 @@ type yamlUnit struct {
 	AddSubfolder     *bool     `yaml:"add_subfolder"`
 	Enabled          *bool     `yaml:"enabled"`
 	UseAbsolutePaths *bool     `yaml:"use_absolute_paths"`
+	FollowSymlinks   *bool     `yaml:"follow_symlinks"`
 }
 
 func (config Config) FromYaml(yamlData []byte) (Config, error) {
@@ -75,6 +77,11 @@ func (config Config) FromYaml(yamlData []byte) (Config, error) {
 			unit.UseAbsolutePaths = *yamlUnit.UseAbsolutePaths
 		}
 
+		unit.FollowSymlinks = false
+		if yamlUnit.FollowSymlinks != nil {
+			unit.FollowSymlinks = *yamlUnit.FollowSymlinks
+		}
+
 		if yamlUnit.Sources == nil || yamlUnit.Destination == nil {
 			log.Fatalf("Sources or destination can't be parsed for unit '%s'", unitName)
 		} else {