cmd/go: work toward build script

The commands in the standard tree are now named
by the pseudo-import paths cmd/gofmt etc.
This avoids ambiguity between cmd/go's directory
and go/token's parent directory.

R=golang-dev, r
CC=golang-dev
https://golang.org/cl/5503050

src/cmd/gc/runtime.go

@@ -6,6 +6,8 @@
 // to update builtin.c.boot.  This is not done automatically
 // to avoid depending on having a working compiler binary.
 
+// +build ignore
+
 package PACKAGE
 
 // emitted by compiler, not referred to by go programs

src/cmd/gc/unsafe.go

@@ -6,6 +6,8 @@
 // to update builtin.c.boot.  This is not done automatically
 // to avoid depending on having a working compiler binary.
 
+// +build ignore
+
 package PACKAGE
 
 type Pointer uintptr // not really; filled in by compiler

src/cmd/go/list.go

@@ -14,7 +14,7 @@ var cmdList = &Command{
 	UsageLine: "list [-f format] [-json] [importpath...]",
 	Short:     "list packages",
 	Long: `
-List lists the packages named by the import paths.
+List lists the packages named by the import paths, one per line.
 
 The default output shows the package name and file system location:
 
@@ -24,7 +24,7 @@ The default output shows the package name and file system location:
 
 The -f flag specifies an alternate format for the list,
 using the syntax of package template.  The default output
-is equivalent to -f '{{.Name}} {{.Dir}}'.  The struct
+is equivalent to -f '{{.ImportPath}}'.  The struct
 being passed to the template is:
 
     type Package struct {
@@ -57,7 +57,7 @@ func init() {
 	cmdList.Run = runList // break init cycle
 }
 
-var listFmt = cmdList.Flag.String("f", "{{.Name}} {{.Dir}}", "")
+var listFmt = cmdList.Flag.String("f", "{{.ImportPath}}", "")
 var listJson = cmdList.Flag.Bool("json", false, "")
 var nl = []byte{'\n'}
 

src/cmd/go/main.go

@@ -237,8 +237,38 @@ func run(cmdline ...string) {
 // allPackages returns all the packages that can be found
 // under the $GOPATH directories and $GOROOT.
 func allPackages() []string {
-	have := make(map[string]bool)
+	have := map[string]bool{
+		"builtin": true, // ignore pseudo-package that exists only for documentation
+	}
 	var pkgs []string
+
+	// Commands
+	goroot := build.Path[0].Path
+	cmd := filepath.Join(goroot, "src/cmd") + string(filepath.Separator)
+	filepath.Walk(cmd, func(path string, fi os.FileInfo, err error) error {
+		if err != nil || !fi.IsDir() {
+			return nil
+		}
+		name := path[len(cmd):]
+		// Commands are all in cmd/, not in subdirectories.
+		if strings.Contains(name, string(filepath.Separator)) {
+			return filepath.SkipDir
+		}
+
+		_, err = build.ScanDir(path)
+		if err != nil {
+			return nil
+		}
+
+		// We use, e.g., cmd/gofmt as the pseudo import path for gofmt.
+		name = "cmd/" + name
+		if !have[name] {
+			have[name] = true
+			pkgs = append(pkgs, name)
+		}
+		return nil
+	})
+
 	for _, t := range build.Path {
 		src := t.SrcDir() + string(filepath.Separator)
 		filepath.Walk(src, func(path string, fi os.FileInfo, err error) error {
@@ -256,21 +286,19 @@ func allPackages() []string {
 				return nil
 			}
 			name := path[len(src):]
-			if have[name] {
-				return nil
-			}
+			if !have[name] {
 				pkgs = append(pkgs, name)
 				have[name] = true
+			}
 
 			// Avoid go/build test data.
+			// TODO: Move it into a testdata directory.
 			if path == filepath.Join(build.Path[0].SrcDir(), "go/build") {
 				return filepath.SkipDir
 			}
 
 			return nil
 		})
-
-		// TODO: Commands.
 	}
 	return pkgs
 }

src/cmd/go/pkg.go

@@ -70,13 +70,15 @@ func loadPackage(arg string) (*Package, error) {
 
 	// Find basic information about package path.
 	t, importPath, err := build.FindTree(arg)
+	dir := ""
 	// Maybe it is a standard command.
-	if err != nil && !filepath.IsAbs(arg) && !strings.HasPrefix(arg, ".") {
+	if err != nil && !filepath.IsAbs(arg) && strings.HasPrefix(arg, "cmd/") {
 		goroot := build.Path[0]
-		p := filepath.Join(goroot.Path, "src/cmd", arg)
+		p := filepath.Join(goroot.Path, "src", arg)
 		if st, err1 := os.Stat(p); err1 == nil && st.IsDir() {
 			t = goroot
-			importPath = "../cmd/" + arg
+			importPath = arg
+			dir = p
 			err = nil
 		}
 	}
@@ -84,7 +86,9 @@ func loadPackage(arg string) (*Package, error) {
 		return nil, err
 	}
 
-	dir := filepath.Join(t.SrcDir(), filepath.FromSlash(importPath))
+	if dir == "" {
+		dir = filepath.Join(t.SrcDir(), filepath.FromSlash(importPath))
+	}
 
 	// Maybe we know the package by its directory.
 	if p := packageCache[dir]; p != nil {
@@ -140,6 +144,13 @@ func scanPackage(ctxt *build.Context, t *build.Tree, arg, importPath, dir string
 	}
 	sort.Strings(p.gofiles)
 
+	// Packages that use cgo import runtime/cgo implicitly,
+	// except runtime/cgo itself.
+	if len(info.CgoFiles) > 0 && (!p.Standard || p.ImportPath != "runtime/cgo") {
+		p.Imports = append(p.Imports, "runtime/cgo")
+		sort.Strings(p.Imports)
+	}
+
 	// Record package under both import path and full directory name.
 	packageCache[dir] = p
 	packageCache[importPath] = p