cli: Restore -lock and -lock-timeout init flags

The -lock and -lock-timeout flags were removed prior to the release of
1.0 as they were thought to have no effect. This is not true in the case
of state migrations when changing backends. This commit restores these
flags, and adds test coverage for locking during backend state
migration.

Also update the help output describing other boolean flags, showing the
argument as the user would type it rather than the default behavior.

internal/command/init.go

@@ -44,6 +44,8 @@ func (c *InitCommand) Run(args []string) int {
 	cmdFlags.StringVar(&flagFromModule, "from-module", "", "copy the source of the given module into the directory before init")
 	cmdFlags.BoolVar(&flagGet, "get", true, "")
 	cmdFlags.BoolVar(&c.forceInitCopy, "force-copy", false, "suppress prompts about copying state data")
+	cmdFlags.BoolVar(&c.Meta.stateLock, "lock", true, "lock state")
+	cmdFlags.DurationVar(&c.Meta.stateLockTimeout, "lock-timeout", 0, "lock timeout")
 	cmdFlags.BoolVar(&c.reconfigure, "reconfigure", false, "reconfigure")
 	cmdFlags.BoolVar(&c.migrateState, "migrate-state", false, "migrate state")
 	cmdFlags.BoolVar(&flagUpgrade, "upgrade", false, "")
@@ -932,6 +934,8 @@ func (c *InitCommand) AutocompleteFlags() complete.Flags {
 		"-from-module":    completePredictModuleSource,
 		"-get":            completePredictBoolean,
 		"-input":          completePredictBoolean,
+		"-lock":           completePredictBoolean,
+		"-lock-timeout":   complete.PredictAnything,
 		"-no-color":       complete.PredictNothing,
 		"-plugin-dir":     complete.PredictDirs(""),
 		"-reconfigure":    complete.PredictNothing,
@@ -959,7 +963,8 @@ Usage: terraform [global options] init [options]
 
 Options:
 
-  -backend=true           Configure the backend for this configuration.
+  -backend=false          Disable backend initialization for this configuration
+                          and use the previously initialized backend instead.
 
   -backend-config=path    This can be either a path to an HCL file with key/value
                           assignments (same format as terraform.tfvars) or a
@@ -975,10 +980,17 @@ Options:
   -from-module=SOURCE     Copy the contents of the given module into the target
                           directory before initialization.
 
-  -get=true               Download any modules for this configuration.
+  -get=false              Disable downloading modules for this configuration.
 
-  -input=true             Ask for input if necessary. If false, will error if
+  -input=false            Disable prompting for missing backend configuration
-                          input was required.
+                          values. This will result in an error if the backend
+                          configuration is not fully specified.
+
+  -lock=false             Don't hold a state lock during backend migration.
+                          This is dangerous if others might concurrently run
+                          commands against the same workspace.
+
+  -lock-timeout=0s        Duration to retry a state lock.
 
   -no-color               If specified, output won't contain any color.
 
@@ -993,9 +1005,10 @@ Options:
   -migrate-state          Reconfigure the backend, and attempt to migrate any
                           existing state.
 
-  -upgrade=false          If installing modules (-get) or plugins, ignore
+  -upgrade                Install the latest module and provider versions
-                          previously-downloaded objects and install the
+                          allowed within configured constraints, overriding the
-                          latest version allowed within configured constraints.
+                          default behavior of selecting exactly the version
+                          recorded in the dependency lockfile.
 
   -lockfile=MODE          Set a dependency lockfile mode.
                           Currently only "readonly" is valid.

internal/command/init_test.go

@@ -562,6 +562,60 @@ func TestInit_backendConfigFileChange(t *testing.T) {
 	}
 }
 
+func TestInit_backendMigrateWhileLocked(t *testing.T) {
+	// Create a temporary working directory that is empty
+	td := tempDir(t)
+	testCopyDir(t, testFixturePath("init-backend-migrate-while-locked"), td)
+	defer os.RemoveAll(td)
+	defer testChdir(t, td)()
+
+	providerSource, close := newMockProviderSource(t, map[string][]string{
+		"hashicorp/test": {"1.2.3"},
+	})
+	defer close()
+
+	ui := new(cli.MockUi)
+	view, _ := testView(t)
+	c := &InitCommand{
+		Meta: Meta{
+			testingOverrides: metaOverridesForProvider(testProvider()),
+			ProviderSource:   providerSource,
+			Ui:               ui,
+			View:             view,
+		},
+	}
+
+	// Create some state, so the backend has something to migrate from
+	f, err := os.Create("local-state.tfstate")
+	if err != nil {
+		t.Fatalf("err: %s", err)
+	}
+	err = writeStateForTesting(testState(), f)
+	f.Close()
+	if err != nil {
+		t.Fatalf("err: %s", err)
+	}
+
+	// Lock the source state
+	unlock, err := testLockState(testDataDir, "local-state.tfstate")
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer unlock()
+
+	// Attempt to migrate
+	args := []string{"-backend-config", "input.config", "-migrate-state", "-force-copy"}
+	if code := c.Run(args); code == 0 {
+		t.Fatalf("expected nonzero exit code: %s", ui.OutputWriter.String())
+	}
+
+	// Disabling locking should work
+	args = []string{"-backend-config", "input.config", "-migrate-state", "-force-copy", "-lock=false"}
+	if code := c.Run(args); code != 0 {
+		t.Fatalf("expected zero exit code, got %d: %s", code, ui.ErrorWriter.String())
+	}
+}
+
 func TestInit_backendConfigKV(t *testing.T) {
 	// Create a temporary working directory that is empty
 	td := tempDir(t)

internal/command/testdata/init-backend-migrate-while-locked/.terraform/terraform.tfstate

@@ -0,0 +1,22 @@
+{
+    "version": 3,
+    "serial": 0,
+    "lineage": "666f9301-7e65-4b19-ae23-71184bb19b03",
+    "backend": {
+        "type": "local",
+        "config": {
+            "path": "local-state.tfstate"
+        },
+        "hash": 9073424445967744180
+    },
+    "modules": [
+        {
+            "path": [
+                "root"
+            ],
+            "outputs": {},
+            "resources": {},
+            "depends_on": []
+        }
+    ]
+}

internal/command/testdata/init-backend-migrate-while-locked/input.config

@@ -0,0 +1 @@
+path = "hello"

internal/command/testdata/init-backend-migrate-while-locked/main.tf

@@ -0,0 +1,5 @@
+terraform {
+  backend "local" {
+    path = "local-state.tfstate"
+  }
+}