Add go-match-context cmd for debugging issues with MatchContext

cmd/go-match-context/.gitignore

@@ -0,0 +1,2 @@
+/go-match-context
+*.exe

cmd/go-match-context/main.go

@@ -0,0 +1,91 @@
+package main
+
+import (
+	"encoding/json"
+	"flag"
+	"fmt"
+	"go/build"
+	"log"
+	"os"
+	"path/filepath"
+
+	"github.com/charlievieth/buildutil"
+)
+
+func init() {
+	log.SetFlags(log.Lshortfile)
+}
+
+type Context struct {
+	GOARCH        string
+	GOOS          string
+	GOROOT        string
+	GOPATH        string
+	Dir           string
+	CgoEnabled    bool
+	UseAllFiles   bool
+	Compiler      string
+	BuildTags     []string
+	ToolTags      []string
+	ReleaseTags   []string
+	InstallSuffix string
+}
+
+func main() {
+	flag.Usage = func() {
+		const usage = "Usage: %s [OPTION] FILE\n" +
+			"MatchContext for FILE and print the new build.Context\n"
+		fmt.Fprintf(os.Stdout, usage, filepath.Base(os.Args[0]))
+		flag.PrintDefaults()
+	}
+	printJSON := flag.Bool("json", false, "Print output as JSON")
+	flag.Parse()
+	if flag.NArg() != 1 {
+		log.Panicln("error: expect one FILE argument")
+		flag.Usage()
+		os.Exit(1)
+	}
+	filename := flag.Arg(0)
+
+	ctxt, err := buildutil.MatchContext(&build.Default, filename, nil)
+	if err != nil {
+		log.Fatal("error:", err)
+	}
+
+	if *printJSON {
+		c := Context{
+			GOARCH:        ctxt.GOARCH,
+			GOOS:          ctxt.GOOS,
+			GOROOT:        ctxt.GOROOT,
+			GOPATH:        ctxt.GOPATH,
+			Dir:           ctxt.Dir,
+			CgoEnabled:    ctxt.CgoEnabled,
+			UseAllFiles:   ctxt.UseAllFiles,
+			Compiler:      ctxt.Compiler,
+			BuildTags:     ctxt.BuildTags,
+			ToolTags:      ctxt.ToolTags,
+			ReleaseTags:   ctxt.ReleaseTags,
+			InstallSuffix: ctxt.InstallSuffix,
+		}
+		data, err := json.MarshalIndent(&c, "", "    ")
+		if err != nil {
+			log.Fatal("error:", err)
+		}
+		if _, err := os.Stdout.Write(data); err != nil {
+			log.Fatal("error:", err)
+		}
+	} else {
+		fmt.Printf("GOARCH=%q\n", ctxt.GOARCH)
+		fmt.Printf("GOOS=%q\n", ctxt.GOOS)
+		fmt.Printf("GOROOT=%q\n", ctxt.GOROOT)
+		fmt.Printf("GOPATH=%q\n", ctxt.GOPATH)
+		fmt.Printf("Dir=%q\n", ctxt.Dir)
+		fmt.Printf("CgoEnabled=%t\n", ctxt.CgoEnabled)
+		fmt.Printf("UseAllFiles=%t\n", ctxt.UseAllFiles)
+		fmt.Printf("Compiler=%q\n", ctxt.Compiler)
+		fmt.Printf("BuildTags=%q\n", ctxt.BuildTags)
+		fmt.Printf("ToolTags=%q\n", ctxt.ToolTags)
+		fmt.Printf("ReleaseTags=%q\n", ctxt.ReleaseTags)
+		fmt.Printf("InstallSuffix=%q\n", ctxt.InstallSuffix)
+	}
+}