cmd/go: accept build flags in clean and list

list has been adding them one at a time haphazardly
(race and tags were there and documented; compiler
was there and undocumented).

clean -i needs -compiler in order to clean the
installed targets for alternate compilers.

Fixes #7302.

While we're here, tweak the language in the 'go get' docs
about build flags.

Fixes #7807.

LGTM=iant
R=golang-codereviews, iant
CC=golang-codereviews
https://golang.org/cl/99130043

src/cmd/go/build.go

@@ -52,7 +52,8 @@ name is the base name of the containing directory.
 
 The -i flag installs the packages that are dependencies of the target.
 
-The build flags are shared by the build, install, run, and test commands:
+The build flags are shared by the build, clean, get, install, list, run,
+and test commands:
 
 	-a
 		force rebuilding of packages that are already up-to-date.
@@ -164,7 +165,8 @@ func init() {
 	}
 }
 
-// addBuildFlags adds the flags common to the build and install commands.
+// addBuildFlags adds the flags common to the build, clean, get,
+// install, list, run, and test commands.
 func addBuildFlags(cmd *Command) {
 	// NOTE: If you add flags here, also add them to testflag.go.
 	cmd.Flag.BoolVar(&buildA, "a", false, "")

src/cmd/go/clean.go

@@ -13,7 +13,7 @@ import (
 )
 
 var cmdClean = &Command{
-	UsageLine: "clean [-i] [-r] [-n] [-x] [packages]",
+	UsageLine: "clean [-i] [-r] [-n] [-x] [build flags] [packages]",
 	Short:     "remove object files",
 	Long: `
 Clean removes object files from package source directories.
@@ -52,23 +52,26 @@ dependencies of the packages named by the import paths.
 
 The -x flag causes clean to print remove commands as it executes them.
 
+For more about build flags, see 'go help build'.
+
 For more about specifying packages, see 'go help packages'.
 	`,
 }
 
 var cleanI bool // clean -i flag
-var cleanN bool // clean -n flag
 var cleanR bool // clean -r flag
-var cleanX bool // clean -x flag
 
 func init() {
 	// break init cycle
 	cmdClean.Run = runClean
 
 	cmdClean.Flag.BoolVar(&cleanI, "i", false, "")
-	cmdClean.Flag.BoolVar(&cleanN, "n", false, "")
 	cmdClean.Flag.BoolVar(&cleanR, "r", false, "")
-	cmdClean.Flag.BoolVar(&cleanX, "x", false, "")
+	// -n and -x are important enough to be
+	// mentioned explicitly in the docs but they
+	// are part of the build flags.
+
+	addBuildFlags(cmdClean)
 }
 
 func runClean(cmd *Command, args []string) {
@@ -169,7 +172,7 @@ func clean(p *Package) {
 		}
 	}
 
-	if cleanN || cleanX {
+	if buildN || buildX {
 		b.showcmd(p.Dir, "rm -f %s", strings.Join(allRemove, " "))
 	}
 
@@ -182,9 +185,9 @@ func clean(p *Package) {
 		if dir.IsDir() {
 			// TODO: Remove once Makefiles are forgotten.
 			if cleanDir[name] {
-				if cleanN || cleanX {
+				if buildN || buildX {
 					b.showcmd(p.Dir, "rm -r %s", name)
-					if cleanN {
+					if buildN {
 						continue
 					}
 				}
@@ -195,7 +198,7 @@ func clean(p *Package) {
 			continue
 		}
 
-		if cleanN {
+		if buildN {
 			continue
 		}
 
@@ -205,10 +208,10 @@ func clean(p *Package) {
 	}
 
 	if cleanI && p.target != "" {
-		if cleanN || cleanX {
+		if buildN || buildX {
 			b.showcmd("", "rm -f %s", p.target)
 		}
-		if !cleanN {
+		if !buildN {
 			removeFile(p.target)
 		}
 	}
@@ -218,10 +221,10 @@ func clean(p *Package) {
 			dir := p.swigDir(&buildContext)
 			soname := p.swigSoname(f)
 			target := filepath.Join(dir, soname)
-			if cleanN || cleanX {
+			if buildN || buildX {
 				b.showcmd("", "rm -f %s", target)
 			}
-			if !cleanN {
+			if !buildN {
 				removeFile(target)
 			}
 		}

src/cmd/go/doc.go

@@ -46,7 +46,7 @@ Compile packages and dependencies
 
 Usage:
 
-	go build [-o output] [build flags] [packages]
+	go build [-o output] [-i] [build flags] [packages]
 
 Build compiles the packages named by the import paths,
 along with their dependencies, but it does not install the results.
@@ -67,6 +67,8 @@ derives from the first file name mentioned, such as f1 for 'go build
 f1.go f2.go'; with no files provided ('go build'), the output file
 name is the base name of the containing directory.
 
+The -i flag installs the packages that are dependencies of the target.
+
 The build flags are shared by the build, install, run, and test commands:
 
 	-a
@@ -122,7 +124,7 @@ Remove object files
 
 Usage:
 
-	go clean [-i] [-r] [-n] [-x] [packages]
+	go clean [-i] [-r] [-n] [-x] [build flags] [packages]
 
 Clean removes object files from package source directories.
 The go command builds most objects in a temporary directory,
@@ -160,6 +162,8 @@ dependencies of the packages named by the import paths.
 
 The -x flag causes clean to print remove commands as it executes them.
 
+For more about build flags, see 'go help build'.
+
 For more about specifying packages, see 'go help packages'.
 
 
@@ -271,7 +275,7 @@ List packages
 
 Usage:
 
-	go list [-e] [-race] [-f format] [-json] [-tags 'tag list'] [packages]
+	go list [-e] [-f format] [-json] [build flags] [packages]
 
 List lists the packages named by the import paths, one per line.
 
@@ -364,11 +368,7 @@ printing.  Erroneous packages will have a non-empty ImportPath and
 a non-nil Error field; other information may or may not be missing
 (zeroed).
 
-The -tags flag specifies a list of build tags, like in the 'go build'
-command.
-
-The -race flag causes the package data to include the dependencies
-required by the race detector.
+For more about build flags, see 'go help build'.
 
 For more about specifying packages, see 'go help packages'.
 

src/cmd/go/get.go

@@ -2,8 +2,6 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-// TODO: Dashboard upload
-
 package main
 
 import (
@@ -37,8 +35,7 @@ The -u flag instructs get to use the network to update the named packages
 and their dependencies.  By default, get uses the network to check out
 missing packages but does not use it to look for updates to existing packages.
 
-Get also accepts all the flags in the 'go build' and 'go install' commands,
-to control the installation. See 'go help build'.
+Get also accepts build flags to control the installation. See 'go help build'.
 
 When checking out or updating a package, get looks for a branch or tag
 that matches the locally installed version of Go. The most important

src/cmd/go/list.go

@@ -14,7 +14,7 @@ import (
 )
 
 var cmdList = &Command{
-	UsageLine: "list [-e] [-race] [-f format] [-json] [-tags 'tag list'] [packages]",
+	UsageLine: "list [-e] [-f format] [-json] [build flags] [packages]",
 	Short:     "list packages",
 	Long: `
 List lists the packages named by the import paths, one per line.
@@ -108,11 +108,7 @@ printing.  Erroneous packages will have a non-empty ImportPath and
 a non-nil Error field; other information may or may not be missing
 (zeroed).
 
-The -tags flag specifies a list of build tags, like in the 'go build'
-command.
-
-The -race flag causes the package data to include the dependencies
-required by the race detector.
+For more about build flags, see 'go help build'.
 
 For more about specifying packages, see 'go help packages'.
 	`,
@@ -120,24 +116,18 @@ For more about specifying packages, see 'go help packages'.
 
 func init() {
 	cmdList.Run = runList // break init cycle
-	cmdList.Flag.Var(buildCompiler{}, "compiler", "")
-	cmdList.Flag.Var((*stringsFlag)(&buildContext.BuildTags), "tags", "")
+	addBuildFlags(cmdList)
 }
 
 var listE = cmdList.Flag.Bool("e", false, "")
 var listFmt = cmdList.Flag.String("f", "{{.ImportPath}}", "")
 var listJson = cmdList.Flag.Bool("json", false, "")
-var listRace = cmdList.Flag.Bool("race", false, "")
 var nl = []byte{'\n'}
 
 func runList(cmd *Command, args []string) {
 	out := newTrackingWriter(os.Stdout)
 	defer out.w.Flush()
 
-	if *listRace {
-		buildRace = true
-	}
-
 	var do func(*Package)
 	if *listJson {
 		do = func(p *Package) {