cmd/go: add go build -i

Fixes #7071.

LGTM=iant
R=golang-codereviews, iant
CC=golang-codereviews
https://golang.org/cl/93770044

src/cmd/go/build.go

@@ -28,7 +28,7 @@ import (
 )
 
 var cmdBuild = &Command{
-	UsageLine: "build [-o output] [build flags] [packages]",
+	UsageLine: "build [-o output] [-i] [build flags] [packages]",
 	Short:     "compile packages and dependencies",
 	Long: `
 Build compiles the packages named by the import paths,
@@ -50,6 +50,8 @@ 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
@@ -107,6 +109,8 @@ func init() {
 	cmdBuild.Run = runBuild
 	cmdInstall.Run = runInstall
 
+	cmdBuild.Flag.BoolVar(&buildI, "i", false, "")
+
 	addBuildFlags(cmdBuild)
 	addBuildFlags(cmdInstall)
 }
@@ -117,6 +121,7 @@ var buildN bool               // -n flag
 var buildP = runtime.NumCPU() // -p flag
 var buildV bool               // -v flag
 var buildX bool               // -x flag
+var buildI bool               // -i flag
 var buildO = cmdBuild.Flag.String("o", "", "output file")
 var buildWork bool           // -work flag
 var buildGcflags []string    // -gcflags flag
@@ -290,8 +295,12 @@ func runBuild(cmd *Command, args []string) {
 	}
 
 	a := &action{}
+	depMode := modeBuild
+	if buildI {
+		depMode = modeInstall
+	}
 	for _, p := range packages(args) {
-		a.deps = append(a.deps, b.action(modeBuild, modeBuild, p))
+		a.deps = append(a.deps, b.action(modeBuild, depMode, p))
 	}
 	b.do(a)
 }

src/cmd/go/test.bash

@@ -708,6 +708,46 @@ if ./testgo test notest >/dev/null 2>&1; then
 fi
 unset GOPATH
 
+TEST list template can use context function
+if ! ./testgo list -f "GOARCH: {{context.GOARCH}}"; then 
+	echo unable to use context in list template
+	ok=false
+fi
+
+TEST build -i installs dependencies
+d=$(TMPDIR=/var/tmp mktemp -d -t testgoXXX)
+export GOPATH=$d
+mkdir -p $d/src/x/y/foo $d/src/x/y/bar
+echo '
+package foo
+func F() {}
+' >$d/src/x/y/foo/foo.go
+echo '
+package bar
+import "x/y/foo"
+func F() { foo.F() }
+' >$d/src/x/y/bar/bar.go
+if ! ./testgo build -v -i x/y/bar &> $d/err; then
+	echo build -i failed
+	cat $d/err
+	ok=false
+elif ! grep x/y/foo $d/err >/dev/null; then
+	echo first build -i did not build x/y/foo
+	cat $d/err
+	ok=false
+fi
+if ! ./testgo build -v -i x/y/bar &> $d/err; then
+	echo second build -i failed
+	cat $d/err
+	ok=false
+elif grep x/y/foo $d/err >/dev/null; then
+	echo second build -i built x/y/foo
+	cat $d/err
+	ok=false
+fi
+rm -rf $d
+unset GOPATH
+
 # clean up
 if $started; then stop; fi
 rm -rf testdata/bin testdata/bin1

src/cmd/go/test.go

@@ -276,7 +276,6 @@ var (
 	testCoverPkgs    []*Package // -coverpkg flag
 	testProfile      bool       // some profiling flag
 	testNeedBinary   bool       // profile needs to keep binary around
-	testI            bool       // -i flag
 	testV            bool       // -v flag
 	testFiles        []string   // -file flag(s)  TODO: not respected
 	testTimeout      string     // -timeout flag
@@ -339,7 +338,7 @@ func runTest(cmd *Command, args []string) {
 	var b builder
 	b.init()
 
-	if testI {
+	if buildI {
 		buildV = testV
 
 		deps := make(map[string]bool)

src/cmd/go/testflag.go

@@ -66,7 +66,6 @@ var testFlagDefn = []*testFlagSpec{
 	// local.
 	{name: "c", boolVar: &testC},
 	{name: "file", multiOK: true},
-	{name: "i", boolVar: &testI},
 	{name: "cover", boolVar: &testCover},
 	{name: "coverpkg"},
 
@@ -75,6 +74,7 @@ var testFlagDefn = []*testFlagSpec{
 	{name: "n", boolVar: &buildN},
 	{name: "p"},
 	{name: "x", boolVar: &buildX},
+	{name: "i", boolVar: &buildI},
 	{name: "work", boolVar: &buildWork},
 	{name: "ccflags"},
 	{name: "gcflags"},