Added exclude patterns support for Clean Task (#274)

* Added exclude patterns support for Clean Task

* Added test file

* Refactoring and cosmetic fixes

* * Replace Match with MatchString

pkg/manager/exclude_files.go

@@ -0,0 +1,89 @@
+package manager
+
+import (
+	"github.com/stashapp/stash/pkg/logger"
+	"regexp"
+	"strings"
+)
+
+func excludeFiles(files []string, patterns []string) ([]string, int) {
+	if patterns == nil {
+		logger.Infof("No exclude patterns in config")
+		return files, 0
+	} else {
+		var results []string
+		var exclCount int
+
+		fileRegexps := generateRegexps(patterns)
+
+		if len(fileRegexps) == 0 {
+			logger.Infof("Excluded 0 files from scan")
+			return files, 0
+		}
+
+		for i := 0; i < len(files); i++ {
+			if matchFileSimple(files[i], fileRegexps) {
+				logger.Infof("File matched pattern. Excluding:\"%s\"", files[i])
+				exclCount++
+			} else {
+
+				//if pattern doesn't match add file to list
+				results = append(results, files[i])
+			}
+		}
+		logger.Infof("Excluded %d file(s) from scan", exclCount)
+		return results, exclCount
+	}
+}
+
+func matchFile(file string, patterns []string) bool {
+	if patterns == nil {
+		logger.Infof("No exclude patterns in config.")
+
+	} else {
+		fileRegexps := generateRegexps(patterns)
+
+		if len(fileRegexps) == 0 {
+			return false
+		}
+
+		for _, regPattern := range fileRegexps {
+			if regPattern.MatchString(strings.ToLower(file)) {
+				return true
+			}
+
+		}
+	}
+
+	return false
+}
+
+func generateRegexps(patterns []string) []*regexp.Regexp {
+
+	var fileRegexps []*regexp.Regexp
+
+	for _, pattern := range patterns {
+		reg, err := regexp.Compile(strings.ToLower(pattern))
+		if err != nil {
+			logger.Errorf("Exclude :%v", err)
+		} else {
+			fileRegexps = append(fileRegexps, reg)
+		}
+	}
+
+	if len(fileRegexps) == 0 {
+		return nil
+	} else {
+		return fileRegexps
+	}
+
+}
+
+func matchFileSimple(file string, regExps []*regexp.Regexp) bool {
+	for _, regPattern := range regExps {
+		if regPattern.MatchString(strings.ToLower(file)) {
+			return true
+		}
+	}
+	return false
+}