cue/load: make cue.mod the default desitination

This effects generation, for instance.

- also update Kubernetes tutorial to use `cue mod init`

Change-Id: I9ff9f023f6771057e86f9f51f6c9c35c095939ce

Closes #168
#168

GitOrigin-RevId: ff720b2
Change-Id: I978632c1697e053c12f51729d6abe9f778b771aa
Reviewed-on: https://cue-review.googlesource.com/c/cue/+/3867
Reviewed-by: Marcel van Lohuizen <mpvl@golang.org>

cue/load/loader_test.go

@@ -89,7 +89,7 @@ err:    relative import paths not allowed ("./file")
 path:   ""
 module: example.org/test
 root:   $CWD/testdata
-dir:    $CWD/testdata/pkg
+dir:    $CWD/testdata/cue.mod/gen
 display:`,
 	}, {
 		cfg:  dirCfg,
@@ -192,7 +192,7 @@ err:    cannot find package "non-existing"
 path:   non-existing
 module: example.org/test
 root:   $CWD/testdata
-dir:    $CWD/testdata/pkg/non-existing
+dir:    $CWD/testdata/cue.mod/gen/non-existing
 display:non-existing`,
 	}, {
 		cfg:  dirCfg,
@@ -216,8 +216,8 @@ display:./imports
 files:
 	$CWD/testdata/imports/imports.cue
 imports:
-	acme.com/catch: $CWD/testdata/pkg/acme.com/catch/catch.cue
-	acme.com/helper:helper1: $CWD/testdata/pkg/acme.com/helper/helper1.cue`,
+	acme.com/catch: $CWD/testdata/cue.mod/pkg/acme.com/catch/catch.cue
+	acme.com/helper:helper1: $CWD/testdata/cue.mod/pkg/acme.com/helper/helper1.cue`,
 	}, {
 		cfg:  dirCfg,
 		args: args("./toolonly"),

doc/tutorial/kubernetes/README.md

@@ -66,23 +66,24 @@ We first make a copy of the data directory.
 
 ```
 $ cp -a original tmp
-$ cd tmp/services
+$ cd tmp
 ```
 
-<!-- TODO
-Although not strictly necessary, we mark the root of the configuration tree
-for good measure.
+We initialize a module so that we can treat all our configuration files
+in the subdirectories as part of one package.
+We do that later by giving all the same package name.
 
 ```
-$ touch ../cue.mod
-cue mod init
+$ cue mod init
 ```
--->
+
+Creating a module also allows our packages import external packages.
 
 Let's try to use the `cue import` command to convert the given YAML files
 into CUE.
 
 ```
+$ cd services
 $ cue import ./...
 Import failed: must specify package name with the -p flag
 ```
@@ -1051,7 +1052,7 @@ $ cue get go k8s.io/api/apps/v1beta1
 
 ```
 
-Now that we have the Kubernetes definitions in `pkg`, we can import and use them:
+Now that we have the Kubernetes definitions in our module, we can import and use them:
 
 ```
 $ cat <<EOF > k8s_defs.cue

doc/tutorial/kubernetes/quick/cue.mod/module.cue

@@ -0,0 +1 @@
+module: ""

doc/tutorial/kubernetes/tut_test.go

@@ -71,6 +71,10 @@ func TestTutorial(t *testing.T) {
 		t.Fatal(err)
 	}
 
+	cuetest.Run(t, dir, "cue mod init", &cuetest.Config{
+		// Stdin: strings.NewReader(input),
+	})
+
 	if *update {
 		// The test environment won't work in all environments. We create
 		// a fake go.mod so that Go will find the module root. By default
@@ -152,6 +156,11 @@ func TestTutorial(t *testing.T) {
 					// Don't execute the kubernetes dry run.
 					break
 				}
+				if strings.HasPrefix(cmd, "cue mod init") {
+					// Already ran this at setup.
+					break
+				}
+
 				if !*update && strings.HasPrefix(cmd, "cue get") {
 					// Don't fetch stuff in normal mode.
 					break