backend/remote: No version check for operations

Terraform remote version conflicts are not a concern for operations. We
are in one of three states:

- Running remotely, in which case the local version is irrelevant;
- Workspace configured for local operations, in which case the remote
  version is meaningless;
- Forcing local operations with a remote backend, which should only
  happen in the Terraform Cloud worker, in which case the Terraform
  versions by definition match.

This commit therefore disables the version check for operations (plan
and apply), which has the consequence of disabling it in Terraform Cloud
and Enterprise runs. In turn this enables Terraform Enterprise runs with
bundles which have a version that doesn't exactly match the bundled
Terraform version.

backend/remote/backend.go

@@ -694,19 +694,22 @@ func (b *Remote) Operation(ctx context.Context, op *backend.Operation) (*backend
 		}
 	}
 
+	// Terraform remote version conflicts are not a concern for operations. We
+	// are in one of three states:
+	//
+	// - Running remotely, in which case the local version is irrelevant;
+	// - Workspace configured for local operations, in which case the remote
+	//   version is meaningless;
+	// - Forcing local operations with a remote backend, which should only
+	//   happen in the Terraform Cloud worker, in which case the Terraform
+	//   versions by definition match.
+	b.IgnoreVersionConflict()
+
 	// Check if we need to use the local backend to run the operation.
 	if b.forceLocal || !w.Operations {
-		if !w.Operations {
-			// Workspace is explicitly configured for local operations, so its
-			// configured Terraform version is meaningless
-			b.IgnoreVersionConflict()
-		}
 		return b.local.Operation(ctx, op)
 	}
 
-	// Running remotely so we don't care about version conflicts
-	b.IgnoreVersionConflict()
-
 	// Set the remote workspace name.
 	op.Workspace = w.Name
 

backend/remote/backend_apply_test.go

@@ -1298,12 +1298,11 @@ func TestRemote_applyVersionCheck(t *testing.T) {
 			remoteVersion: "0.13.5",
 			hasOperations: false,
 		},
-		"error if force local, has remote operations, different versions": {
+		"force local with remote operations and different versions is acceptable": {
 			localVersion:  "0.14.0",
-			remoteVersion: "0.13.5",
+			remoteVersion: "0.14.0-acme-provider-bundle",
 			forceLocal:    true,
 			hasOperations: true,
-			wantErr:       `Remote workspace Terraform version "0.13.5" does not match local Terraform version "0.14.0"`,
 		},
 		"no error if versions are identical": {
 			localVersion:  "0.14.0",