Add a method to discover if a library is being modified

To be in isBeingModified state, a library must:
- have one of its file modified in the last 24 hours
- have a time difference between oldest and newest file bigger than 5 minutes (aka, the lib has not just been extracted from a zip)

libraries_loader.go

@@ -30,9 +30,12 @@
 package builder
 
 import (
+	"math"
 	"os"
 	"path/filepath"
+	"strconv"
 	"strings"
+	"time"
 
 	"github.com/arduino/arduino-builder/constants"
 	"github.com/arduino/arduino-builder/i18n"
@@ -153,6 +156,11 @@ func makeNewLibrary(libraryFolder string, debugLevel int, logger i18n.Logger) (*
 		return nil, i18n.WrapError(err)
 	}
 
+	timeDiff, newestFile := newestAndOldestFileDifferBy(libraryFolder)
+	if timeDiff > (5*time.Minute) && time.Since(newestFile) < 24*time.Hour {
+		library.IsBeingModified = true
+	}
+
 	if debugLevel >= 0 {
 		for _, subFolder := range subFolders {
 			if utils.IsSCCSOrHiddenFile(subFolder) {
@@ -220,3 +228,22 @@ func appendPathToLibrariesFolders(librariesFolders []string, newLibrariesFolder
 
 	return utils.AppendIfNotPresent(librariesFolders, newLibrariesFolder)
 }
+
+func newestAndOldestFileDifferBy(path string) (time.Duration, time.Time) {
+	var newestTime int64 = 0
+	var oldestTime int64 = math.MaxInt64
+
+	filepath.Walk(path,
+		func(path string, info os.FileInfo, err error) error {
+			currTime := info.ModTime().Unix()
+			if currTime > newestTime {
+				newestTime = currTime
+			}
+			if currTime < oldestTime {
+				oldestTime = currTime
+			}
+			return nil
+		})
+	duration, _ := time.ParseDuration(strconv.FormatInt(newestTime-oldestTime, 10) + "s")
+	return duration, time.Unix(newestTime, 0)
+}

types/types.go

@@ -162,26 +162,27 @@ const (
 )
 
 type Library struct {
-	Folder        string
-	SrcFolder     string
-	UtilityFolder string
-	Layout        LibraryLayout
-	Name          string
-	RealName      string
-	Archs         []string
-	DotALinkage   bool
-	Precompiled   bool
-	LDflags       string
-	IsLegacy      bool
-	Version       string
-	Author        string
-	Maintainer    string
-	Sentence      string
-	Paragraph     string
-	URL           string
-	Category      string
-	License       string
-	Properties    map[string]string
+	Folder          string
+	SrcFolder       string
+	UtilityFolder   string
+	Layout          LibraryLayout
+	Name            string
+	RealName        string
+	Archs           []string
+	DotALinkage     bool
+	Precompiled     bool
+	LDflags         string
+	IsLegacy        bool
+	Version         string
+	Author          string
+	Maintainer      string
+	Sentence        string
+	Paragraph       string
+	URL             string
+	Category        string
+	License         string
+	Properties      map[string]string
+	IsBeingModified bool
 }
 
 func (library *Library) String() string {