diff --git a/CHANGELOG.md b/CHANGELOG.md
index 2481d3dbc..5374b9973 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,3 +1,12 @@
+## 1.7.0 / 2020-06-17
+
+* [CHANGE] API client: Add start/end parameters to `LabelNames` and `LabelValues`. #767
+* [FEATURE] testutil: Add `GatherAndCount` and enable filtering in `CollectAndCount` #753
+* [FEATURE] API client: Add support for `status` and `runtimeinfo` endpoints. #755
+* [ENHANCEMENT] Wrapping `nil` with a `WrapRegistererWith...` function creates a no-op `Registerer`.  #764
+* [ENHANCEMENT] promlint: Allow Kelvin as a base unit for cases like color temperature. #761
+* [BUGFIX] push: Properly handle empty job and label values. #752
+
 ## 1.6.0 / 2020-04-28
 
 * [FEATURE] testutil: Add lint checks for metrics, including a sub-package `promlint` to expose the linter engine for external usage. #739 #743
diff --git a/Makefile b/Makefile
index b25fb8358..f35cf5868 100644
--- a/Makefile
+++ b/Makefile
@@ -13,13 +13,6 @@
 
 include Makefile.common
 
-# http.CloseNotifier is deprecated but we don't want to remove support
-# from client_golang to not break anybody still using it.
-STATICCHECK_IGNORE = \
-  github.com/prometheus/client_golang/prometheus/promhttp/delegator*.go:SA1019 \
-  github.com/prometheus/client_golang/prometheus/promhttp/instrument_server_test.go:SA1019 \
-  github.com/prometheus/client_golang/prometheus/http.go:SA1019
-
 .PHONY: test
 test: deps common-test
 
diff --git a/Makefile.common b/Makefile.common
index b978dfc50..9320176ca 100644
--- a/Makefile.common
+++ b/Makefile.common
@@ -150,6 +150,17 @@ else
 	$(GO) get $(GOOPTS) -t ./...
 endif
 
+.PHONY: update-go-deps
+update-go-deps:
+	@echo ">> updating Go dependencies"
+	@for m in $$($(GO) list -mod=readonly -m -f '{{ if and (not .Indirect) (not .Main)}}{{.Path}}{{end}}' all); do \
+		$(GO) get $$m; \
+	done
+	GO111MODULE=$(GO111MODULE) $(GO) mod tidy
+ifneq (,$(wildcard vendor))
+	GO111MODULE=$(GO111MODULE) $(GO) mod vendor
+endif
+
 .PHONY: common-test-short
 common-test-short: $(GOTEST_DIR)
 	@echo ">> running short tests"
diff --git a/VERSION b/VERSION
index dc1e644a1..bd8bf882d 100644
--- a/VERSION
+++ b/VERSION
@@ -1 +1 @@
-1.6.0
+1.7.0
diff --git a/api/prometheus/v1/api.go b/api/prometheus/v1/api.go
index fa35dddee..b77294778 100644
--- a/api/prometheus/v1/api.go
+++ b/api/prometheus/v1/api.go
@@ -137,6 +137,7 @@ const (
 	epCleanTombstones = apiPrefix + "/admin/tsdb/clean_tombstones"
 	epConfig          = apiPrefix + "/status/config"
 	epFlags           = apiPrefix + "/status/flags"
+	epRuntimeinfo     = apiPrefix + "/status/runtimeinfo"
 )
 
 // AlertState models the state of an alert.
@@ -231,13 +232,15 @@ type API interface {
 	// Flags returns the flag values that Prometheus was launched with.
 	Flags(ctx context.Context) (FlagsResult, error)
 	// LabelNames returns all the unique label names present in the block in sorted order.
-	LabelNames(ctx context.Context) ([]string, Warnings, error)
+	LabelNames(ctx context.Context, startTime time.Time, endTime time.Time) ([]string, Warnings, error)
 	// LabelValues performs a query for the values of the given label.
-	LabelValues(ctx context.Context, label string) (model.LabelValues, Warnings, error)
+	LabelValues(ctx context.Context, label string, startTime time.Time, endTime time.Time) (model.LabelValues, Warnings, error)
 	// Query performs a query for the given time.
 	Query(ctx context.Context, query string, ts time.Time) (model.Value, Warnings, error)
 	// QueryRange performs a query for the given range.
 	QueryRange(ctx context.Context, query string, r Range) (model.Value, Warnings, error)
+	// Runtimeinfo returns the various runtime information properties about the Prometheus server.
+	Runtimeinfo(ctx context.Context) (RuntimeinfoResult, error)
 	// Series finds series by label matchers.
 	Series(ctx context.Context, matches []string, startTime time.Time, endTime time.Time) ([]model.LabelSet, Warnings, error)
 	// Snapshot creates a snapshot of all current data into snapshots/<datetime>-<rand>
@@ -277,6 +280,22 @@ type ConfigResult struct {
 // FlagsResult contains the result from querying the flag endpoint.
 type FlagsResult map[string]string
 
+// RuntimeinfoResult contains the result from querying the runtimeinfo endpoint.
+type RuntimeinfoResult struct {
+	StartTime           string `json:"startTime"`
+	CWD                 string `json:"CWD"`
+	ReloadConfigSuccess bool   `json:"reloadConfigSuccess"`
+	LastConfigTime      string `json:"lastConfigTime"`
+	ChunkCount          int    `json:"chunkCount"`
+	TimeSeriesCount     int    `json:"timeSeriesCount"`
+	CorruptionCount     int    `json:"corruptionCount"`
+	GoroutineCount      int    `json:"goroutineCount"`
+	GOMAXPROCS          int    `json:"GOMAXPROCS"`
+	GOGC                string `json:"GOGC"`
+	GODEBUG             string `json:"GODEBUG"`
+	StorageRetention    string `json:"storageRetention"`
+}
+
 // SnapshotResult contains the result from querying the snapshot endpoint.
 type SnapshotResult struct {
 	Name string `json:"name"`
@@ -640,8 +659,29 @@ func (h *httpAPI) Flags(ctx context.Context) (FlagsResult, error) {
 	return res, json.Unmarshal(body, &res)
 }
 
-func (h *httpAPI) LabelNames(ctx context.Context) ([]string, Warnings, error) {
+func (h *httpAPI) Runtimeinfo(ctx context.Context) (RuntimeinfoResult, error) {
+	u := h.client.URL(epRuntimeinfo, nil)
+
+	req, err := http.NewRequest(http.MethodGet, u.String(), nil)
+	if err != nil {
+		return RuntimeinfoResult{}, err
+	}
+
+	_, body, _, err := h.client.Do(ctx, req)
+	if err != nil {
+		return RuntimeinfoResult{}, err
+	}
+
+	var res RuntimeinfoResult
+	return res, json.Unmarshal(body, &res)
+}
+
+func (h *httpAPI) LabelNames(ctx context.Context, startTime time.Time, endTime time.Time) ([]string, Warnings, error) {
 	u := h.client.URL(epLabels, nil)
+	q := u.Query()
+	q.Set("start", formatTime(startTime))
+	q.Set("end", formatTime(endTime))
+
 	req, err := http.NewRequest(http.MethodGet, u.String(), nil)
 	if err != nil {
 		return nil, nil, err
@@ -654,8 +694,12 @@ func (h *httpAPI) LabelNames(ctx context.Context) ([]string, Warnings, error) {
 	return labelNames, w, json.Unmarshal(body, &labelNames)
 }
 
-func (h *httpAPI) LabelValues(ctx context.Context, label string) (model.LabelValues, Warnings, error) {
+func (h *httpAPI) LabelValues(ctx context.Context, label string, startTime time.Time, endTime time.Time) (model.LabelValues, Warnings, error) {
 	u := h.client.URL(epLabelValues, map[string]string{"name": label})
+	q := u.Query()
+	q.Set("start", formatTime(startTime))
+	q.Set("end", formatTime(endTime))
+
 	req, err := http.NewRequest(http.MethodGet, u.String(), nil)
 	if err != nil {
 		return nil, nil, err
diff --git a/api/prometheus/v1/api_test.go b/api/prometheus/v1/api_test.go
index b36c380c7..4bc4d53f5 100644
--- a/api/prometheus/v1/api_test.go
+++ b/api/prometheus/v1/api_test.go
@@ -144,15 +144,22 @@ func TestAPIs(t *testing.T) {
 		}
 	}
 
+	doRuntimeinfo := func() func() (interface{}, Warnings, error) {
+		return func() (interface{}, Warnings, error) {
+			v, err := promAPI.Runtimeinfo(context.Background())
+			return v, nil, err
+		}
+	}
+
 	doLabelNames := func(label string) func() (interface{}, Warnings, error) {
 		return func() (interface{}, Warnings, error) {
-			return promAPI.LabelNames(context.Background())
+			return promAPI.LabelNames(context.Background(), time.Now().Add(-100*time.Hour), time.Now())
 		}
 	}
 
 	doLabelValues := func(label string) func() (interface{}, Warnings, error) {
 		return func() (interface{}, Warnings, error) {
-			return promAPI.LabelValues(context.Background(), label)
+			return promAPI.LabelValues(context.Background(), label, time.Now().Add(-100*time.Hour), time.Now())
 		}
 	}
 
@@ -605,6 +612,48 @@ func TestAPIs(t *testing.T) {
 			err:       fmt.Errorf("some error"),
 		},
 
+		{
+			do:        doRuntimeinfo(),
+			reqMethod: "GET",
+			reqPath:   "/api/v1/status/runtimeinfo",
+			inErr:     fmt.Errorf("some error"),
+			err:       fmt.Errorf("some error"),
+		},
+
+		{
+			do:        doRuntimeinfo(),
+			reqMethod: "GET",
+			reqPath:   "/api/v1/status/runtimeinfo",
+			inRes: map[string]interface{}{
+				"startTime":           "2020-05-18T15:52:53.4503113Z",
+				"CWD":                 "/prometheus",
+				"reloadConfigSuccess": true,
+				"lastConfigTime":      "2020-05-18T15:52:56Z",
+				"chunkCount":          72692,
+				"timeSeriesCount":     18476,
+				"corruptionCount":     0,
+				"goroutineCount":      217,
+				"GOMAXPROCS":          2,
+				"GOGC":                "100",
+				"GODEBUG":             "allocfreetrace",
+				"storageRetention":    "1d",
+			},
+			res: RuntimeinfoResult{
+				StartTime:           "2020-05-18T15:52:53.4503113Z",
+				CWD:                 "/prometheus",
+				ReloadConfigSuccess: true,
+				LastConfigTime:      "2020-05-18T15:52:56Z",
+				ChunkCount:          72692,
+				TimeSeriesCount:     18476,
+				CorruptionCount:     0,
+				GoroutineCount:      217,
+				GOMAXPROCS:          2,
+				GOGC:                "100",
+				GODEBUG:             "allocfreetrace",
+				StorageRetention:    "1d",
+			},
+		},
+
 		{
 			do:        doAlertManagers(),
 			reqMethod: "GET",
diff --git a/go.mod b/go.mod
index 61b13edc7..c91a43318 100644
--- a/go.mod
+++ b/go.mod
@@ -3,14 +3,14 @@ module github.com/prometheus/client_golang
 require (
 	github.com/beorn7/perks v1.0.1
 	github.com/cespare/xxhash/v2 v2.1.1
-	github.com/golang/protobuf v1.4.0
-	github.com/json-iterator/go v1.1.9
+	github.com/golang/protobuf v1.4.2
+	github.com/json-iterator/go v1.1.10
 	github.com/kr/pretty v0.1.0 // indirect
 	github.com/prometheus/client_model v0.2.0
-	github.com/prometheus/common v0.9.1
-	github.com/prometheus/procfs v0.0.11
+	github.com/prometheus/common v0.10.0
+	github.com/prometheus/procfs v0.1.3
 	github.com/stretchr/testify v1.4.0 // indirect
-	golang.org/x/sys v0.0.0-20200420163511-1957bb5e6d1f
+	golang.org/x/sys v0.0.0-20200615200032-f1bc736245b1
 	gopkg.in/check.v1 v1.0.0-20190902080502-41f04d3bba15 // indirect
 	gopkg.in/yaml.v2 v2.2.5 // indirect
 )
diff --git a/go.sum b/go.sum
index 8932e64d7..1b92f6ebf 100644
--- a/go.sum
+++ b/go.sum
@@ -37,6 +37,8 @@ github.com/golang/protobuf v1.4.0-rc.2/go.mod h1:LlEzMj4AhA7rCAGe4KMBDvJI+AwstrU
 github.com/golang/protobuf v1.4.0-rc.4.0.20200313231945-b860323f09d0/go.mod h1:WU3c8KckQ9AFe+yFwt9sWVRKCVIyN9cPHBJSNnbL67w=
 github.com/golang/protobuf v1.4.0 h1:oOuy+ugB+P/kBdUnG5QaMXSIyJ1q38wWSojYCb3z5VQ=
 github.com/golang/protobuf v1.4.0/go.mod h1:jodUvKwWbYaEsadDk5Fwe5c77LiNKVO9IDvqG2KuDX0=
+github.com/golang/protobuf v1.4.2 h1:+Z5KGCizgyZCbGh1KZqA0fcLLkwbsjIzS4aV2v7wJX0=
+github.com/golang/protobuf v1.4.2/go.mod h1:oDoupMAO8OvCJWAcko0GGGIgR6R6ocIYbsSw735rRwI=
 github.com/google/go-cmp v0.3.0/go.mod h1:8QqcDgzrUqlUb/G2PQTWiueGozuR1884gddMywk6iLU=
 github.com/google/go-cmp v0.3.1 h1:Xye71clBPdm5HgqGwUkwhbynsUJZhDbS20FvLhQ2izg=
 github.com/google/go-cmp v0.3.1/go.mod h1:8QqcDgzrUqlUb/G2PQTWiueGozuR1884gddMywk6iLU=
@@ -46,8 +48,8 @@ github.com/google/gofuzz v1.0.0 h1:A8PeW59pxE9IoFRqBp37U+mSNaQoZ46F1f0f863XSXw=
 github.com/google/gofuzz v1.0.0/go.mod h1:dBl0BpW6vV/+mYPU4Po3pmUjxk6FQPldtuIdl/M65Eg=
 github.com/json-iterator/go v1.1.6 h1:MrUvLMLTMxbqFJ9kzlvat/rYZqZnW3u4wkLzWTaFwKs=
 github.com/json-iterator/go v1.1.6/go.mod h1:+SdeFBvtyEkXs7REEP0seUULqWtbJapLOCVDaaPEHmU=
-github.com/json-iterator/go v1.1.9 h1:9yzud/Ht36ygwatGx56VwCZtlI/2AD15T1X2sjSuGns=
-github.com/json-iterator/go v1.1.9/go.mod h1:KdQUCv79m/52Kvf8AW2vK1V8akMuk1QjK/uOdHXbAo4=
+github.com/json-iterator/go v1.1.10 h1:Kz6Cvnvv2wGdaG/V8yMvfkmNiXq9Ya2KUv4rouJJr68=
+github.com/json-iterator/go v1.1.10/go.mod h1:KdQUCv79m/52Kvf8AW2vK1V8akMuk1QjK/uOdHXbAo4=
 github.com/julienschmidt/httprouter v1.2.0/go.mod h1:SYymIcj16QtmaHHD7aYtjjsJG7VTCxuUUipMqKk8s4w=
 github.com/konsorten/go-windows-terminal-sequences v1.0.1/go.mod h1:T0+1ngSBFLxvqU3pZ+m/2kptfBszLMUkC4ZK/EgS/cQ=
 github.com/kr/logfmt v0.0.0-20140226030751-b84e30acd515 h1:T+h1c/A9Gawja4Y9mFVWj2vyii2bbUNDw3kt9VxK2EY=
@@ -82,13 +84,13 @@ github.com/prometheus/client_model v0.2.0 h1:uq5h0d+GuxiXLJLNABMgp2qUWDPiLvgCzz2
 github.com/prometheus/client_model v0.2.0/go.mod h1:xMI15A0UPsDsEKsMN9yxemIoYk6Tm2C1GtYGdfGttqA=
 github.com/prometheus/common v0.4.1 h1:K0MGApIoQvMw27RTdJkPbr3JZ7DNbtxQNyi5STVM6Kw=
 github.com/prometheus/common v0.4.1/go.mod h1:TNfzLD0ON7rHzMJeJkieUDPYmFC7Snx/y86RQel1bk4=
-github.com/prometheus/common v0.9.1 h1:KOMtN28tlbam3/7ZKEYKHhKoJZYYj3gMH4uc62x7X7U=
-github.com/prometheus/common v0.9.1/go.mod h1:yhUN8i9wzaXS3w1O07YhxHEBxD+W35wd8bs7vj7HSQ4=
+github.com/prometheus/common v0.10.0 h1:RyRA7RzGXQZiW+tGMr7sxa85G1z0yOpM1qq5c8lNawc=
+github.com/prometheus/common v0.10.0/go.mod h1:Tlit/dnDKsSWFlCLTWaA1cyBgKHSMdTB80sz/V91rCo=
 github.com/prometheus/procfs v0.0.0-20181005140218-185b4288413d/go.mod h1:c3At6R/oaqEKCNdg8wHV1ftS6bRYblBhIjjI8uT2IGk=
 github.com/prometheus/procfs v0.0.2 h1:6LJUbpNm42llc4HRCuvApCSWB/WfhuNo9K98Q9sNGfs=
 github.com/prometheus/procfs v0.0.2/go.mod h1:TjEm7ze935MbeOT/UhFTIMYKhuLP4wbCsTZCD3I8kEA=
-github.com/prometheus/procfs v0.0.11 h1:DhHlBtkHWPYi8O2y31JkK0TF+DGM+51OopZjH/Ia5qI=
-github.com/prometheus/procfs v0.0.11/go.mod h1:lV6e/gmhEcM9IjHGsFOCxxuZ+z1YqCvr4OA4YeYWdaU=
+github.com/prometheus/procfs v0.1.3 h1:F0+tqvhOksq22sc6iCHF5WGlWjdwj92p0udFh1VFBS8=
+github.com/prometheus/procfs v0.1.3/go.mod h1:lV6e/gmhEcM9IjHGsFOCxxuZ+z1YqCvr4OA4YeYWdaU=
 github.com/sirupsen/logrus v1.2.0/go.mod h1:LxeOpSwHxABJmUn/MG1IvRgCAasNZTLOkJPxbbu5VWo=
 github.com/sirupsen/logrus v1.4.2 h1:SPIRibHv4MatM3XXNO2BJeFLZwZ2LvZgfQ5+UNI2im4=
 github.com/sirupsen/logrus v1.4.2/go.mod h1:tLMulIdttU9McNUspp0xgXVQah82FyeX6MwdIuYE2rE=
@@ -116,8 +118,8 @@ golang.org/x/sys v0.0.0-20181116152217-5ac8a444bdc5/go.mod h1:STP8DvDyc/dI5b8T5h
 golang.org/x/sys v0.0.0-20190215142949-d0b11bdaac8a/go.mod h1:STP8DvDyc/dI5b8T5hshtkjS+E42TnysNCUPdjciGhY=
 golang.org/x/sys v0.0.0-20190422165155-953cdadca894/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
 golang.org/x/sys v0.0.0-20200106162015-b016eb3dc98e/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
-golang.org/x/sys v0.0.0-20200420163511-1957bb5e6d1f h1:gWF768j/LaZugp8dyS4UwsslYCYz9XgFxvlgsn0n9H8=
-golang.org/x/sys v0.0.0-20200420163511-1957bb5e6d1f/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
+golang.org/x/sys v0.0.0-20200615200032-f1bc736245b1 h1:ogLJMz+qpzav7lGMh10LMvAkM/fAoGlaiiHYiFYdm80=
+golang.org/x/sys v0.0.0-20200615200032-f1bc736245b1/go.mod h1:h1NjWce9XRLGQEsW7wpKNCjG9DtNlClVuFLEZdDNbEs=
 golang.org/x/text v0.3.0/go.mod h1:NqM8EUOU14njkJ3fqMW+pc6Ldnwhi/IjpwHt7yyuwOQ=
 golang.org/x/xerrors v0.0.0-20191204190536-9bdfabe68543 h1:E7g+9GITq07hpfrRu66IVDexMakfv52eLZ2CXBWiKr4=
 golang.org/x/xerrors v0.0.0-20191204190536-9bdfabe68543/go.mod h1:I/5z698sn9Ka8TeJc9MKroUUfqBBauWjQqLJ2OPfmY0=
@@ -127,6 +129,8 @@ google.golang.org/protobuf v0.0.0-20200228230310-ab0ca4ff8a60/go.mod h1:cfTl7dwQ
 google.golang.org/protobuf v1.20.1-0.20200309200217-e05f789c0967/go.mod h1:A+miEFZTKqfCUM6K7xSMQL9OKL/b6hQv+e19PK+JZNE=
 google.golang.org/protobuf v1.21.0 h1:qdOKuR/EIArgaWNjetjgTzgVTAZ+S/WXVrq9HW9zimw=
 google.golang.org/protobuf v1.21.0/go.mod h1:47Nbq4nVaFHyn7ilMalzfO3qCViNmqZ2kzikPIcrTAo=
+google.golang.org/protobuf v1.23.0 h1:4MY060fB1DLGMB/7MBTLnwQUY6+F09GEiz6SsrNqyzM=
+google.golang.org/protobuf v1.23.0/go.mod h1:EGpADcykh3NcUnDUJcl1+ZksZNG86OlYog2l/sGQquU=
 gopkg.in/alecthomas/kingpin.v2 v2.2.6 h1:jMFz6MfLP0/4fUyZle81rXUoxOBFi19VUFKVDOQfozc=
 gopkg.in/alecthomas/kingpin.v2 v2.2.6/go.mod h1:FMv+mEhP44yOT+4EoQTLFTRgOQ1FBLkstjWtayDeSgw=
 gopkg.in/check.v1 v0.0.0-20161208181325-20d25e280405/go.mod h1:Co6ibVJAznAaIkqp8huTwlJQCZ016jof/cbN4VW5Yz0=
diff --git a/prometheus/counter_test.go b/prometheus/counter_test.go
index e2e31fcf7..56652a0a0 100644
--- a/prometheus/counter_test.go
+++ b/prometheus/counter_test.go
@@ -19,6 +19,7 @@ import (
 	"testing"
 	"time"
 
+	//lint:ignore SA1019 Need to keep deprecated package for compatibility.
 	"github.com/golang/protobuf/proto"
 	"github.com/golang/protobuf/ptypes"
 
diff --git a/prometheus/desc.go b/prometheus/desc.go
index e3232d79f..2f19f5e1e 100644
--- a/prometheus/desc.go
+++ b/prometheus/desc.go
@@ -20,6 +20,7 @@ import (
 	"strings"
 
 	"github.com/cespare/xxhash/v2"
+	//lint:ignore SA1019 Need to keep deprecated package for compatibility.
 	"github.com/golang/protobuf/proto"
 	"github.com/prometheus/common/model"
 
diff --git a/prometheus/examples_test.go b/prometheus/examples_test.go
index 903d4d978..8bc051af7 100644
--- a/prometheus/examples_test.go
+++ b/prometheus/examples_test.go
@@ -22,6 +22,7 @@ import (
 	"strings"
 	"time"
 
+	//lint:ignore SA1019 Need to keep deprecated package for compatibility.
 	"github.com/golang/protobuf/proto"
 	"github.com/prometheus/common/expfmt"
 
diff --git a/prometheus/histogram.go b/prometheus/histogram.go
index 4271f438a..3a5aac700 100644
--- a/prometheus/histogram.go
+++ b/prometheus/histogram.go
@@ -22,6 +22,7 @@ import (
 	"sync/atomic"
 	"time"
 
+	//lint:ignore SA1019 Need to keep deprecated package for compatibility.
 	"github.com/golang/protobuf/proto"
 
 	dto "github.com/prometheus/client_model/go"
diff --git a/prometheus/histogram_test.go b/prometheus/histogram_test.go
index 2e8f4b8c1..0b4826c56 100644
--- a/prometheus/histogram_test.go
+++ b/prometheus/histogram_test.go
@@ -24,6 +24,7 @@ import (
 	"testing/quick"
 	"time"
 
+	//lint:ignore SA1019 Need to keep deprecated package for compatibility.
 	"github.com/golang/protobuf/proto"
 	"github.com/golang/protobuf/ptypes"
 
diff --git a/prometheus/metric.go b/prometheus/metric.go
index 0df1eff88..35bd8bde3 100644
--- a/prometheus/metric.go
+++ b/prometheus/metric.go
@@ -17,6 +17,7 @@ import (
 	"strings"
 	"time"
 
+	//lint:ignore SA1019 Need to keep deprecated package for compatibility.
 	"github.com/golang/protobuf/proto"
 	"github.com/prometheus/common/model"
 
diff --git a/prometheus/promauto/auto.go b/prometheus/promauto/auto.go
index 3c10c8524..f8d50d1f9 100644
--- a/prometheus/promauto/auto.go
+++ b/prometheus/promauto/auto.go
@@ -98,7 +98,7 @@
 //        	requestCount = promauto.With(reg).NewCounterVec(
 //        		prometheus.CounterOpts{
 //        			Name: "http_requests_total",
-//        			Help: "Total number of HTTP requests by status code end method.",
+//        			Help: "Total number of HTTP requests by status code and method.",
 //        		},
 //        		[]string{"code", "method"},
 //        	)
@@ -117,7 +117,7 @@
 //        	requestCount = factory.NewCounterVec(
 //        		prometheus.CounterOpts{
 //        			Name: "http_requests_total",
-//        			Help: "Total number of HTTP requests by status code end method.",
+//        			Help: "Total number of HTTP requests by status code and method.",
 //        		},
 //        		[]string{"code", "method"},
 //        	)
@@ -127,29 +127,30 @@
 // separate package?
 //
 // The main problem is that registration may fail, e.g. if a metric inconsistent
-// with the newly to be registered one is already registered. Therefore, the
-// Register method in the prometheus.Registerer interface returns an error, and
-// the same is the case for the top-level prometheus.Register function that
-// registers with the global registry. The prometheus package also provides
-// MustRegister versions for both. They panic if the registration fails, and
-// they clearly call this out by using the Must… idiom. Panicking is a bit
-// problematic here because it doesn't just happen on input provided by the
-// caller that is invalid on its own. Things are a bit more subtle here: Metric
-// creation and registration tend to be spread widely over the codebase. It can
-// easily happen that an incompatible metric is added to an unrelated part of
-// the code, and suddenly code that used to work perfectly fine starts to panic
-// (provided that the registration of the newly added metric happens before the
-// registration of the previously existing metric). This may come as an even
-// bigger surprise with the global registry, where simply importing another
-// package can trigger a panic (if the newly imported package registers metrics
-// in its init function). At least, in the prometheus package, creation of
-// metrics and other collectors is separate from registration. You first create
-// the metric, and then you decide explicitly if you want to register it with a
-// local or the global registry, and if you want to handle the error or risk a
-// panic. With the constructors in the promauto package, registration is
-// automatic, and if it fails, it will always panic. Furthermore, the
-// constructors will often be called in the var section of a file, which means
-// that panicking will happen as a side effect of merely importing a package.
+// with or equal to the newly to be registered one is already registered.
+// Therefore, the Register method in the prometheus.Registerer interface returns
+// an error, and the same is the case for the top-level prometheus.Register
+// function that registers with the global registry. The prometheus package also
+// provides MustRegister versions for both. They panic if the registration
+// fails, and they clearly call this out by using the Must…  idiom. Panicking is
+// problematic in this case because it doesn't just happen on input provided by
+// the caller that is invalid on its own. Things are a bit more subtle here:
+// Metric creation and registration tend to be spread widely over the
+// codebase. It can easily happen that an incompatible metric is added to an
+// unrelated part of the code, and suddenly code that used to work perfectly
+// fine starts to panic (provided that the registration of the newly added
+// metric happens before the registration of the previously existing
+// metric). This may come as an even bigger surprise with the global registry,
+// where simply importing another package can trigger a panic (if the newly
+// imported package registers metrics in its init function). At least, in the
+// prometheus package, creation of metrics and other collectors is separate from
+// registration. You first create the metric, and then you decide explicitly if
+// you want to register it with a local or the global registry, and if you want
+// to handle the error or risk a panic. With the constructors in the promauto
+// package, registration is automatic, and if it fails, it will always
+// panic. Furthermore, the constructors will often be called in the var section
+// of a file, which means that panicking will happen as a side effect of merely
+// importing a package.
 //
 // A separate package allows conservative users to entirely ignore it. And
 // whoever wants to use it, will do so explicitly, with an opportunity to read
@@ -252,7 +253,8 @@ type Factory struct {
 }
 
 // With creates a Factory using the provided Registerer for registration of the
-// created Collectors.
+// created Collectors. If the provided Registerer is nil, the returned Factory
+// creates Collectors that are not registered with any Registerer.
 func With(r prometheus.Registerer) Factory { return Factory{r} }
 
 // NewCounter works like the function of the same name in the prometheus package
diff --git a/prometheus/promauto/auto_test.go b/prometheus/promauto/auto_test.go
new file mode 100644
index 000000000..44805cb73
--- /dev/null
+++ b/prometheus/promauto/auto_test.go
@@ -0,0 +1,25 @@
+// Copyright 2020 The Prometheus Authors
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package promauto
+
+import (
+	"testing"
+
+	"github.com/prometheus/client_golang/prometheus"
+)
+
+func TestNil(t *testing.T) {
+	// A nil registerer should be treated as a no-op by promauto.
+	With(nil).NewCounter(prometheus.CounterOpts{Name: "test"}).Inc()
+}
diff --git a/prometheus/push/push.go b/prometheus/push/push.go
index 77ce9c837..c1a6cb99f 100644
--- a/prometheus/push/push.go
+++ b/prometheus/push/push.go
@@ -37,6 +37,7 @@ package push
 import (
 	"bytes"
 	"encoding/base64"
+	"errors"
 	"fmt"
 	"io/ioutil"
 	"net/http"
@@ -56,6 +57,8 @@ const (
 	base64Suffix = "@base64"
 )
 
+var errJobEmpty = errors.New("job name is empty")
+
 // HTTPDoer is an interface for the one method of http.Client that is used by Pusher
 type HTTPDoer interface {
 	Do(*http.Request) (*http.Response, error)
@@ -80,14 +83,17 @@ type Pusher struct {
 }
 
 // New creates a new Pusher to push to the provided URL with the provided job
-// name. You can use just host:port or ip:port as url, in which case “http://”
-// is added automatically. Alternatively, include the schema in the
-// URL. However, do not include the “/metrics/jobs/…” part.
+// name (which must not be empty). You can use just host:port or ip:port as url,
+// in which case “http://” is added automatically. Alternatively, include the
+// schema in the URL. However, do not include the “/metrics/jobs/…” part.
 func New(url, job string) *Pusher {
 	var (
 		reg = prometheus.NewRegistry()
 		err error
 	)
+	if job == "" {
+		err = errJobEmpty
+	}
 	if !strings.Contains(url, "://") {
 		url = "http://" + url
 	}
@@ -267,7 +273,7 @@ func (p *Pusher) push(method string) error {
 		return err
 	}
 	defer resp.Body.Close()
-	// Pushgateway 0.10+ responds with StatusOK, earlier versions with StatusAccepted.
+	// Depending on version and configuration of the PGW, StatusOK or StatusAccepted may be returned.
 	if resp.StatusCode != http.StatusOK && resp.StatusCode != http.StatusAccepted {
 		body, _ := ioutil.ReadAll(resp.Body) // Ignore any further error as this is for an error message only.
 		return fmt.Errorf("unexpected status code %d while pushing to %s: %s", resp.StatusCode, p.fullURL(), body)
@@ -278,9 +284,11 @@ func (p *Pusher) push(method string) error {
 // fullURL assembles the URL used to push/delete metrics and returns it as a
 // string. The job name and any grouping label values containing a '/' will
 // trigger a base64 encoding of the affected component and proper suffixing of
-// the preceding component. If the component does not contain a '/' but other
-// special character, the usual url.QueryEscape is used for compatibility with
-// older versions of the Pushgateway and for better readability.
+// the preceding component. Similarly, an empty grouping label value will be
+// encoded as base64 just with a single `=` padding character (to avoid an empty
+// path component). If the component does not contain a '/' but other special
+// characters, the usual url.QueryEscape is used for compatibility with older
+// versions of the Pushgateway and for better readability.
 func (p *Pusher) fullURL() string {
 	urlComponents := []string{}
 	if encodedJob, base64 := encodeComponent(p.job); base64 {
@@ -299,9 +307,12 @@ func (p *Pusher) fullURL() string {
 }
 
 // encodeComponent encodes the provided string with base64.RawURLEncoding in
-// case it contains '/'. If not, it uses url.QueryEscape instead. It returns
-// true in the former case.
+// case it contains '/' and as "=" in case it is empty. If neither is the case,
+// it uses url.QueryEscape instead. It returns true in the former two cases.
 func encodeComponent(s string) (string, bool) {
+	if s == "" {
+		return "=", true
+	}
 	if strings.Contains(s, "/") {
 		return base64.RawURLEncoding.EncodeToString([]byte(s)), true
 	}
diff --git a/prometheus/push/push_test.go b/prometheus/push/push_test.go
index 1fabe39c6..99155b0ed 100644
--- a/prometheus/push/push_test.go
+++ b/prometheus/push/push_test.go
@@ -176,6 +176,36 @@ func TestPush(t *testing.T) {
 		t.Error("unexpected path:", lastPath)
 	}
 
+	// Empty label value triggers special base64 encoding.
+	if err := New(pgwOK.URL, "testjob").
+		Grouping("empty", "").
+		Collector(metric1).
+		Collector(metric2).
+		Push(); err != nil {
+		t.Fatal(err)
+	}
+	if lastMethod != http.MethodPut {
+		t.Errorf("got method %q for Push, want %q", lastMethod, http.MethodPut)
+	}
+	if !bytes.Equal(lastBody, wantBody) {
+		t.Errorf("got body %v, want %v", lastBody, wantBody)
+	}
+	if lastPath != "/metrics/job/testjob/empty@base64/=" {
+		t.Error("unexpected path:", lastPath)
+	}
+
+	// Empty job name results in error.
+	if err := New(pgwErr.URL, "").
+		Collector(metric1).
+		Collector(metric2).
+		Push(); err == nil {
+		t.Error("push with empty job succeded")
+	} else {
+		if got, want := err, errJobEmpty; got != want {
+			t.Errorf("got error %q, want %q", got, want)
+		}
+	}
+
 	// Push some Collectors with a broken PGW.
 	if err := New(pgwErr.URL, "testjob").
 		Collector(metric1).
@@ -251,5 +281,4 @@ func TestPush(t *testing.T) {
 	if lastPath != "/metrics/job/testjob/a/x/b/y" && lastPath != "/metrics/job/testjob/b/y/a/x" {
 		t.Error("unexpected path:", lastPath)
 	}
-
 }
diff --git a/prometheus/registry.go b/prometheus/registry.go
index c05d6ee1b..ba94405af 100644
--- a/prometheus/registry.go
+++ b/prometheus/registry.go
@@ -26,6 +26,7 @@ import (
 	"unicode/utf8"
 
 	"github.com/cespare/xxhash/v2"
+	//lint:ignore SA1019 Need to keep deprecated package for compatibility.
 	"github.com/golang/protobuf/proto"
 	"github.com/prometheus/common/expfmt"
 
diff --git a/prometheus/registry_test.go b/prometheus/registry_test.go
index 67e4fcbc9..48596cd72 100644
--- a/prometheus/registry_test.go
+++ b/prometheus/registry_test.go
@@ -33,6 +33,7 @@ import (
 
 	dto "github.com/prometheus/client_model/go"
 
+	//lint:ignore SA1019 Need to keep deprecated package for compatibility.
 	"github.com/golang/protobuf/proto"
 	"github.com/prometheus/common/expfmt"
 
diff --git a/prometheus/summary.go b/prometheus/summary.go
index ae42e761a..f3c1440d1 100644
--- a/prometheus/summary.go
+++ b/prometheus/summary.go
@@ -23,6 +23,7 @@ import (
 	"time"
 
 	"github.com/beorn7/perks/quantile"
+	//lint:ignore SA1019 Need to keep deprecated package for compatibility.
 	"github.com/golang/protobuf/proto"
 
 	dto "github.com/prometheus/client_model/go"
diff --git a/prometheus/testutil/promlint/promlint.go b/prometheus/testutil/promlint/promlint.go
index e48e4d453..ec8061706 100644
--- a/prometheus/testutil/promlint/promlint.go
+++ b/prometheus/testutil/promlint/promlint.go
@@ -313,9 +313,10 @@ var (
 		// Base units.
 		"amperes": "amperes",
 		"bytes":   "bytes",
-		"celsius": "celsius", // Celsius is more common in practice than Kelvin.
+		"celsius": "celsius", // Also allow Celsius because it is common in typical Prometheus use cases.
 		"grams":   "grams",
 		"joules":  "joules",
+		"kelvin":  "kelvin", // SI base unit, used in special cases (e.g. color temperature, scientific measurements).
 		"meters":  "meters", // Both American and international spelling permitted.
 		"metres":  "metres",
 		"seconds": "seconds",
@@ -328,8 +329,7 @@ var (
 		"days":    "seconds",
 		"weeks":   "seconds",
 		// Temperature.
-		"kelvin":     "celsius",
-		"kelvins":    "celsius",
+		"kelvins":    "kelvin",
 		"fahrenheit": "celsius",
 		"rankine":    "celsius",
 		// Length.
diff --git a/prometheus/testutil/promlint/promlint_test.go b/prometheus/testutil/promlint/promlint_test.go
index c2d9980c4..f545322c6 100644
--- a/prometheus/testutil/promlint/promlint_test.go
+++ b/prometheus/testutil/promlint/promlint_test.go
@@ -164,6 +164,14 @@ x_seconds 10
 # HELP x_joules Test metric.
 # TYPE x_joules untyped
 x_joules 10
+`,
+		},
+		{
+			name: "kelvin",
+			in: `
+# HELP x_kelvin Test metric.
+# TYPE x_kelvin untyped
+x_kelvin 10
 `,
 		},
 		// bad cases.
@@ -287,18 +295,6 @@ x_days 10
 				Text:   `use base unit "seconds" instead of "days"`,
 			}},
 		},
-		{
-			name: "kelvin",
-			in: `
-# HELP x_kelvin Test metric.
-# TYPE x_kelvin untyped
-x_kelvin 10
-`,
-			problems: []promlint.Problem{{
-				Metric: "x_kelvin",
-				Text:   `use base unit "celsius" instead of "kelvin"`,
-			}},
-		},
 		{
 			name: "kelvins",
 			in: `
@@ -308,7 +304,7 @@ x_kelvins 10
 `,
 			problems: []promlint.Problem{{
 				Metric: "x_kelvins",
-				Text:   `use base unit "celsius" instead of "kelvins"`,
+				Text:   `use base unit "kelvin" instead of "kelvins"`,
 			}},
 		},
 		{
diff --git a/prometheus/testutil/testutil.go b/prometheus/testutil/testutil.go
index c47373c0b..9af60ce1d 100644
--- a/prometheus/testutil/testutil.go
+++ b/prometheus/testutil/testutil.go
@@ -112,31 +112,43 @@ func ToFloat64(c prometheus.Collector) float64 {
 	panic(fmt.Errorf("collected a non-gauge/counter/untyped metric: %s", pb))
 }
 
-// CollectAndCount collects all Metrics from the provided Collector and returns their number.
-//
-// This can be used to assert the number of metrics collected by a given collector after certain operations.
-//
-// This function is only for testing purposes, and even for testing, other approaches
-// are often more appropriate (see this package's documentation).
-func CollectAndCount(c prometheus.Collector) int {
-	var (
-		mCount int
-		mChan  = make(chan prometheus.Metric)
-		done   = make(chan struct{})
-	)
-
-	go func() {
-		for range mChan {
-			mCount++
-		}
-		close(done)
-	}()
+// CollectAndCount registers the provided Collector with a newly created
+// pedantic Registry. It then calls GatherAndCount with that Registry and with
+// the provided metricNames. In the unlikely case that the registration or the
+// gathering fails, this function panics. (This is inconsistent with the other
+// CollectAnd… functions in this package and has historical reasons. Changing
+// the function signature would be a breaking change and will therefore only
+// happen with the next major version bump.)
+func CollectAndCount(c prometheus.Collector, metricNames ...string) int {
+	reg := prometheus.NewPedanticRegistry()
+	if err := reg.Register(c); err != nil {
+		panic(fmt.Errorf("registering collector failed: %s", err))
+	}
+	result, err := GatherAndCount(reg, metricNames...)
+	if err != nil {
+		panic(err)
+	}
+	return result
+}
 
-	c.Collect(mChan)
-	close(mChan)
-	<-done
+// GatherAndCount gathers all metrics from the provided Gatherer and counts
+// them. It returns the number of metric children in all gathered metric
+// families together. If any metricNames are provided, only metrics with those
+// names are counted.
+func GatherAndCount(g prometheus.Gatherer, metricNames ...string) (int, error) {
+	got, err := g.Gather()
+	if err != nil {
+		return 0, fmt.Errorf("gathering metrics failed: %s", err)
+	}
+	if metricNames != nil {
+		got = filterMetrics(got, metricNames)
+	}
 
-	return mCount
+	result := 0
+	for _, mf := range got {
+		result += len(mf.GetMetric())
+	}
+	return result, nil
 }
 
 // CollectAndCompare registers the provided Collector with a newly created
diff --git a/prometheus/testutil/testutil_test.go b/prometheus/testutil/testutil_test.go
index aaf670786..56d993382 100644
--- a/prometheus/testutil/testutil_test.go
+++ b/prometheus/testutil/testutil_test.go
@@ -306,3 +306,30 @@ some_total{label1="value1"} 1
 		t.Errorf("Expected\n%#+v\nGot:\n%#+v", expectedError, err.Error())
 	}
 }
+
+func TestCollectAndCount(t *testing.T) {
+	c := prometheus.NewCounterVec(
+		prometheus.CounterOpts{
+			Name: "some_total",
+			Help: "A value that represents a counter.",
+		},
+		[]string{"foo"},
+	)
+	if got, want := CollectAndCount(c), 0; got != want {
+		t.Errorf("unexpected metric count, got %d, want %d", got, want)
+	}
+	c.WithLabelValues("bar")
+	if got, want := CollectAndCount(c), 1; got != want {
+		t.Errorf("unexpected metric count, got %d, want %d", got, want)
+	}
+	c.WithLabelValues("baz")
+	if got, want := CollectAndCount(c), 2; got != want {
+		t.Errorf("unexpected metric count, got %d, want %d", got, want)
+	}
+	if got, want := CollectAndCount(c, "some_total"), 2; got != want {
+		t.Errorf("unexpected metric count, got %d, want %d", got, want)
+	}
+	if got, want := CollectAndCount(c, "some_other_total"), 0; got != want {
+		t.Errorf("unexpected metric count, got %d, want %d", got, want)
+	}
+}
diff --git a/prometheus/value.go b/prometheus/value.go
index 2be470ce1..6206928cc 100644
--- a/prometheus/value.go
+++ b/prometheus/value.go
@@ -19,6 +19,7 @@ import (
 	"time"
 	"unicode/utf8"
 
+	//lint:ignore SA1019 Need to keep deprecated package for compatibility.
 	"github.com/golang/protobuf/proto"
 	"github.com/golang/protobuf/ptypes"
 
diff --git a/prometheus/wrap.go b/prometheus/wrap.go
index e303eef6d..438aa5e92 100644
--- a/prometheus/wrap.go
+++ b/prometheus/wrap.go
@@ -17,6 +17,7 @@ import (
 	"fmt"
 	"sort"
 
+	//lint:ignore SA1019 Need to keep deprecated package for compatibility.
 	"github.com/golang/protobuf/proto"
 
 	dto "github.com/prometheus/client_model/go"
@@ -27,7 +28,8 @@ import (
 // registered with the wrapped Registerer in a modified way. The modified
 // Collector adds the provided Labels to all Metrics it collects (as
 // ConstLabels). The Metrics collected by the unmodified Collector must not
-// duplicate any of those labels.
+// duplicate any of those labels. Wrapping a nil value is valid, resulting
+// in a no-op Registerer.
 //
 // WrapRegistererWith provides a way to add fixed labels to a subset of
 // Collectors. It should not be used to add fixed labels to all metrics exposed.
@@ -50,6 +52,7 @@ func WrapRegistererWith(labels Labels, reg Registerer) Registerer {
 // Registerer. Collectors registered with the returned Registerer will be
 // registered with the wrapped Registerer in a modified way. The modified
 // Collector adds the provided prefix to the name of all Metrics it collects.
+// Wrapping a nil value is valid, resulting in a no-op Registerer.
 //
 // WrapRegistererWithPrefix is useful to have one place to prefix all metrics of
 // a sub-system. To make this work, register metrics of the sub-system with the
@@ -80,6 +83,9 @@ type wrappingRegisterer struct {
 }
 
 func (r *wrappingRegisterer) Register(c Collector) error {
+	if r.wrappedRegisterer == nil {
+		return nil
+	}
 	return r.wrappedRegisterer.Register(&wrappingCollector{
 		wrappedCollector: c,
 		prefix:           r.prefix,
@@ -88,6 +94,9 @@ func (r *wrappingRegisterer) Register(c Collector) error {
 }
 
 func (r *wrappingRegisterer) MustRegister(cs ...Collector) {
+	if r.wrappedRegisterer == nil {
+		return
+	}
 	for _, c := range cs {
 		if err := r.Register(c); err != nil {
 			panic(err)
@@ -96,6 +105,9 @@ func (r *wrappingRegisterer) MustRegister(cs ...Collector) {
 }
 
 func (r *wrappingRegisterer) Unregister(c Collector) bool {
+	if r.wrappedRegisterer == nil {
+		return false
+	}
 	return r.wrappedRegisterer.Unregister(&wrappingCollector{
 		wrappedCollector: c,
 		prefix:           r.prefix,
diff --git a/prometheus/wrap_test.go b/prometheus/wrap_test.go
index 0fbb78c04..003544e31 100644
--- a/prometheus/wrap_test.go
+++ b/prometheus/wrap_test.go
@@ -19,6 +19,7 @@ import (
 	"strings"
 	"testing"
 
+	//lint:ignore SA1019 Need to keep deprecated package for compatibility.
 	"github.com/golang/protobuf/proto"
 
 	dto "github.com/prometheus/client_model/go"
@@ -320,3 +321,12 @@ func TestWrap(t *testing.T) {
 	}
 
 }
+
+func TestNil(t *testing.T) {
+	// A wrapped nil registerer should be treated as a no-op, and not panic.
+	c := NewCounter(CounterOpts{Name: "test"})
+	err := WrapRegistererWith(Labels{"foo": "bar"}, nil).Register(c)
+	if err != nil {
+		t.Fatal("registering failed:", err)
+	}
+}