allow go install knative.dev/func@{version} (#2220)

Makefile

@@ -28,7 +28,7 @@ VTAG         := $(shell [ -z $(VTAG) ] && echo $(ETAG) || echo $(VTAG))
 VERS         ?= $(shell git describe --tags --match 'v*')
 KVER         ?= $(shell git describe --tags --match 'knative-*')
 
-LDFLAGS      := -X main.date=$(DATE) -X main.vers=$(VERS) -X main.kver=$(KVER) -X main.hash=$(HASH)
+LDFLAGS      := -X knative.dev/func/pkg/app.vers=$(VERS) -X knative.dev/func/pkg/app.kver=$(KVER) -X knative.dev/func/pkg/app.hash=$(HASH)
 ifneq ($(FUNC_REPO_REF),)
   LDFLAGS      += -X knative.dev/func/pkg/pipelines/tekton.FuncRepoRef=$(FUNC_REPO_REF)
 endif
@@ -202,7 +202,7 @@ test-integration: ## Run integration tests using an available cluster.
 .PHONY: func-instrumented
 
 func-instrumented: ## Func binary that is instrumented for e2e tests
-	env CGO_ENABLED=1 go build -ldflags "$(LDFLAGS)" -cover -o func ./cmd/func
+	env CGO_ENABLED=1 go build -ldflags "$(LDFLAGS)" -cover -o func ./cmd/$(BIN)
 
 test-e2e: func-instrumented ## Run end-to-end tests using an available cluster.
 	./test/e2e_extended_tests.sh

cmd/func/main.go

@@ -1,73 +1,7 @@
 package main
 
-import (
-	"context"
-	"errors"
-	"fmt"
-	"os"
-	"os/exec"
-	"os/signal"
-	"syscall"
-
-	"github.com/AlecAivazis/survey/v2/terminal"
-	"knative.dev/func/cmd"
-	"knative.dev/func/pkg/docker"
-)
-
-// Statically-populated build metadata set by `make build`.
-var vers, kver, hash string
+import "knative.dev/func/pkg/app"
 
 func main() {
-	ctx, cancel := context.WithCancel(context.Background())
-	defer cancel()
-
-	sigs := make(chan os.Signal, 1)
-	signal.Notify(sigs, syscall.SIGINT, syscall.SIGTERM)
-	go func() {
-		<-sigs
-		cancel()
-		<-sigs // second sigint/sigterm is treated as sigkill
-		os.Exit(137)
-	}()
-
-	cfg := cmd.RootCommandConfig{
-		Name: "func",
-		Version: cmd.Version{
-			Vers: vers,
-			Kver: kver,
-			Hash: hash,
-		}}
-
-	if err := cmd.NewRootCmd(cfg).ExecuteContext(ctx); err != nil {
-		if !errors.Is(err, terminal.InterruptErr) {
-			fmt.Fprintf(os.Stderr, "Error: %v\n", err)
-		}
-		if ctx.Err() != nil || errors.Is(err, terminal.InterruptErr) {
-			os.Exit(130)
-		}
-
-		if errors.Is(err, docker.ErrNoDocker) {
-			if !dockerOrPodmanInstalled() {
-				fmt.Fprintln(os.Stderr, `Docker/Podman not installed.
-Please consider installing one of these:
-  https://podman-desktop.io/
-  https://www.docker.com/products/docker-desktop/`)
-			} else {
-				fmt.Fprintln(os.Stderr, `Possible causes:
-  The docker/podman daemon is not running.
-  The DOCKER_HOST environment variable is not set.`)
-			}
-		}
-
-		os.Exit(1)
-	}
-}
-
-func dockerOrPodmanInstalled() bool {
-	_, err := exec.LookPath("podman")
-	if err == nil {
-		return true
-	}
-	_, err = exec.LookPath("docker")
-	return err == nil
+	app.Main()
 }

main.go

@@ -0,0 +1,7 @@
+package main
+
+import "knative.dev/func/pkg/app"
+
+func main() {
+	app.Main()
+}

pkg/app/app.go

@@ -0,0 +1,72 @@
+package app
+
+import (
+	"context"
+	"errors"
+	"fmt"
+	"os"
+	"os/exec"
+	"os/signal"
+	"syscall"
+
+	"github.com/AlecAivazis/survey/v2/terminal"
+	"knative.dev/func/cmd"
+	"knative.dev/func/pkg/docker"
+)
+
+var vers, kver, hash string
+
+func Main() {
+	ctx, cancel := context.WithCancel(context.Background())
+	defer cancel()
+
+	sigs := make(chan os.Signal, 1)
+	signal.Notify(sigs, syscall.SIGINT, syscall.SIGTERM)
+	go func() {
+		<-sigs
+		cancel()
+		<-sigs // second sigint/sigterm is treated as sigkill
+		os.Exit(137)
+	}()
+
+	cfg := cmd.RootCommandConfig{
+		Name: "func",
+		Version: cmd.Version{
+			Vers: vers,
+			Kver: kver,
+			Hash: hash,
+		}}
+
+	if err := cmd.NewRootCmd(cfg).ExecuteContext(ctx); err != nil {
+		if !errors.Is(err, terminal.InterruptErr) {
+			fmt.Fprintf(os.Stderr, "Error: %v\n", err)
+		}
+		if ctx.Err() != nil || errors.Is(err, terminal.InterruptErr) {
+			os.Exit(130)
+		}
+
+		if errors.Is(err, docker.ErrNoDocker) {
+			if !dockerOrPodmanInstalled() {
+				fmt.Fprintln(os.Stderr, `Docker/Podman not installed.
+Please consider installing one of these:
+  https://podman-desktop.io/
+  https://www.docker.com/products/docker-desktop/`)
+			} else {
+				fmt.Fprintln(os.Stderr, `Possible causes:
+  The docker/podman daemon is not running.
+  The DOCKER_HOST environment variable is not set.`)
+			}
+		}
+
+		os.Exit(1)
+	}
+}
+
+func dockerOrPodmanInstalled() bool {
+	_, err := exec.LookPath("podman")
+	if err == nil {
+		return true
+	}
+	_, err = exec.LookPath("docker")
+	return err == nil
+}