Remove unused func, var, and const (#928)

Signed-off-by: Mario Trangoni <mjtrangoni@gmail.com>

collector/collector.go

@@ -42,10 +42,6 @@ var (
 	)
 )
 
-func warnDeprecated(collector string) {
-	log.Warnf("The %s collector is deprecated and will be removed in the future!", collector)
-}
-
 const (
 	defaultEnabled  = true
 	defaultDisabled = false

collector/cpu_linux.go

@@ -19,7 +19,6 @@ import (
 	"fmt"
 	"os"
 	"path/filepath"
-	"regexp"
 	"strconv"
 	"strings"
 
@@ -28,10 +27,6 @@ import (
 	"github.com/prometheus/procfs"
 )
 
-var (
-	digitRegexp = regexp.MustCompile("[0-9]+")
-)
-
 type cpuCollector struct {
 	cpu                *prometheus.Desc
 	cpuGuest           *prometheus.Desc

collector/textfile.go

@@ -22,7 +22,6 @@ import (
 	"path/filepath"
 	"sort"
 	"strings"
-	"sync"
 	"time"
 
 	"github.com/prometheus/client_golang/prometheus"
@@ -34,7 +33,6 @@ import (
 
 var (
 	textFileDirectory = kingpin.Flag("collector.textfile.directory", "Directory to read text files with metrics from.").Default("").String()
-	textFileAddOnce   sync.Once
 	mtimeDesc         = prometheus.NewDesc(
 		"node_textfile_mtime_seconds",
 		"Unixtime mtime of textfiles successfully read.",