Add godoc-style docstrings to Cmd... methods

Signed-off-by: Peggy Li <peggyli.224@gmail.com>
Upstream-commit: b5d0380108dde9e96d51bb01821860a0799dee0d
Component: engine

components/engine/api/client/exec.go

@@ -12,6 +12,9 @@ import (
 	"github.com/docker/docker/utils"
 )
 
+// CmdExec runs a command in a running container.
+//
+// Usage: docker exec [OPTIONS] CONTAINER COMMAND [ARG...]
 func (cli *DockerCli) CmdExec(args ...string) error {
 	cmd := cli.Subcmd("exec", "CONTAINER COMMAND [ARG...]", "Run a command in a running container", true)