cli: Add -ignore-remote-version flag for init

When performing state migration to a remote backend target, Terraform
may fail due to mismatched remote and local Terraform versions. Here we
add the `-ignore-remote-version` flag to allow users to ignore this
version check when necessary.

internal/command/init.go

@@ -49,6 +49,7 @@ func (c *InitCommand) Run(args []string) int {
 	cmdFlags.BoolVar(&flagUpgrade, "upgrade", false, "")
 	cmdFlags.Var(&flagPluginPath, "plugin-dir", "plugin directory")
 	cmdFlags.StringVar(&flagLockfile, "lockfile", "", "Set a dependency lockfile mode")
+	cmdFlags.BoolVar(&c.Meta.ignoreRemoteVersion, "ignore-remote-version", false, "continue even if remote and local Terraform versions are incompatible")
 	cmdFlags.Usage = func() { c.Ui.Error(c.Help()) }
 	if err := cmdFlags.Parse(args); err != nil {
 		return 1
@@ -1003,6 +1004,9 @@ Options:
   -lockfile=MODE          Set a dependency lockfile mode.
                           Currently only "readonly" is valid.
 
+  -ignore-remote-version  A rare option used for the remote backend only. See
+                          the remote backend documentation for more information.
+
 `
 	return strings.TrimSpace(helpText)
 }