document epochs

docs/src/training/training.md

@@ -76,3 +76,19 @@ evalcb() = @show(loss(test_x, test_y))
 Flux.train!(objective, data, opt,
             cb = throttle(evalcb, 5))
 ```
+
+Note that, by default, `train!` only loops over the data once (a single "epoch").
+A convenient way to run multiple epochs from the REPL is provided by `@epochs`.
+
+```julia
+julia> using Flux: @epochs
+
+julia> @epochs 2 println("hello")
+INFO: Epoch 1
+hello
+INFO: Epoch 2
+hello
+
+julia> @epochs 2 Flux.train!(...)
+# Train for two epochs
+```