Deprecate train command with warning before future removal (#2818)

* deprecate train command with warning before future removal

* chore: fmt

Signed-off-by: Mark Phelps <mphelps@cloudflare.com>

---------

Signed-off-by: Mark Phelps <mphelps@cloudflare.com>

Author: markphelps

integration-tests/tests/train_deprecated.txtar

@@ -0,0 +1,13 @@
+# Test that the train command shows a deprecation warning
+
+# Train command should fail (no cog.yaml) but still show deprecation warning
+! cog train
+stderr 'Command "train" is deprecated'
+stderr 'will be removed in a future version of Cog'
+
+-- predict.py --
+from cog import BasePredictor
+
+class Predictor(BasePredictor):
+    def predict(self, s: str) -> str:
+        return "hello " + s

pkg/cli/train.go

@@ -33,9 +33,10 @@ If 'image' is passed, it will run the training on that Docker image.
 It must be an image that has been built by Cog.
 
 Otherwise, it will build the model in the current directory and train it.`,
-		RunE:   cmdTrain,
-		Args:   cobra.MaximumNArgs(1),
-		Hidden: true,
+		RunE:       cmdTrain,
+		Args:       cobra.MaximumNArgs(1),
+		Hidden:     true,
+		Deprecated: "the train command will be removed in a future version of Cog",
 	}
 
 	addBuildProgressOutputFlag(cmd)

pkg/cli/train_test.go

@@ -0,0 +1,13 @@
+package cli
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/require"
+)
+
+func TestTrainCommandIsDeprecated(t *testing.T) {
+	cmd := newTrainCommand()
+	require.NotEmpty(t, cmd.Deprecated, "train command should have a deprecation message")
+	require.Contains(t, cmd.Deprecated, "will be removed in a future version")
+}