update init docs for -migrate-state

command/init.go

@@ -933,6 +933,7 @@ func (c *InitCommand) AutocompleteFlags() complete.Flags {
 		"-no-color":       complete.PredictNothing,
 		"-plugin-dir":     complete.PredictDirs(""),
 		"-reconfigure":    complete.PredictNothing,
+		"-migrate-state":  complete.PredictNothing,
 		"-upgrade":        completePredictBoolean,
 	}
 }
@@ -987,6 +988,9 @@ Options:
   -reconfigure         Reconfigure the backend, ignoring any saved
                        configuration.
 
+  -migrate-state       Reconfigure the backend, and attempt to migrate any
+                       existing state.
+
   -upgrade=false       If installing modules (-get) or plugins, ignore
                        previously-downloaded objects and install the
                        latest version allowed within configured constraints.

website/docs/cli/commands/init.html.md

@@ -79,11 +79,17 @@ During init, the root configuration directory is consulted for
 is initialized using the given configuration settings.
 
 Re-running init with an already-initialized backend will update the working
-directory to use the new backend settings. Depending on what changed, this
-may result in interactive prompts to confirm migration of workspace states.
-The `-force-copy` option suppresses these prompts and answers "yes" to the
-migration questions. The `-reconfigure` option disregards any existing
-configuration, preventing migration of any existing state.
+directory to use the new backend settings. Either `-reconfigure` or
+`-migrate-state` must be supplied to update the backend configuration. 
+
+The `-migrate-state` option will attempt to copy existing state to the new
+backend, and depending on what changed, may result in interactive prompts to
+confirm migration of workspace states.  The `-force-copy` option suppresses
+these prompts and answers "yes" to the migration questions. This implies
+`-migrate-state`.
+
+The `-reconfigure` option disregards any existing configuration, preventing
+migration of any existing state.
 
 To skip backend configuration, use `-backend=false`. Note that some other init
 steps require an initialized backend, so it is recommended to use this flag only