build: misc make check improvements

Makefile

@@ -165,7 +165,7 @@ check:
 	# compile everything; go vet sometimes reports incorrect errors if
 	# the build artifacts are stale.
 	$(GO) test -i -tags '$(TAGS)' ./...
-	$(GO) test ./build -v -tags check
+	$(GO) test ./build -v -tags check -run 'TestStyle/$(TESTS)'
 
 .PHONY: clean
 clean:

build/style_test.go

@@ -23,6 +23,7 @@ import (
 	"os"
 	"os/exec"
 	"path/filepath"
+	"strconv"
 	"strings"
 	"testing"
 
@@ -445,6 +446,19 @@ func TestStyle(t *testing.T) {
 				t.Fatalf("err=%s, stderr=%s", err, out)
 			}
 		}
+
+		if t.Failed() {
+			args := append([]string(nil), cmd.Args[1:len(cmd.Args)-1]...)
+			args = append(args, "-w", ".")
+			for i := range args {
+				args[i] = strconv.Quote(args[i])
+			}
+			t.Logf("run the following to fix your formatting:\n"+
+				"\n%s %s\n\n"+
+				"Don't forget to add amend the result to the correct commits.",
+				cmd.Args[0], strings.Join(args, " "),
+			)
+		}
 	})
 
 	t.Run("TestVet", func(t *testing.T) {
@@ -482,7 +496,7 @@ func TestStyle(t *testing.T) {
 		switch err := cmd.Run(); err.(type) {
 		case nil:
 		case *exec.ExitError:
-			t.Log(err) // Non-zero exit is expected.
+			// Non-zero exit is expected.
 		default:
 			t.Fatal(err)
 		}

githooks/pre-push

@@ -0,0 +1,3 @@
+#!/usr/bin/env sh
+
+make check TESTS=TestCrlfmt