Move resize after attaching

Resize by +1 when attaching to force redrawing.

Start monitoring window size after the attach begins instead of before. This way, you see the output
from the container without having to manually resize or hit enter. This makes attach consistent with
run and exec.

Signed-off-by: Andy Goldstein <agoldste@redhat.com>

api/client/attach.go

@@ -41,12 +41,6 @@ func (cli *DockerCli) CmdAttach(args ...string) error {
 		return err
 	}
 
-	if c.Config.Tty && cli.isTerminalOut {
-		if err := cli.monitorTtySize(cmd.Arg(0), false); err != nil {
-			logrus.Debugf("Error monitoring TTY size: %s", err)
-		}
-	}
-
 	if *detachKeys != "" {
 		cli.configFile.DetachKeys = *detachKeys
 	}
@@ -82,6 +76,21 @@ func (cli *DockerCli) CmdAttach(args ...string) error {
 		defer cli.restoreTerminal(in)
 	}
 
+	if c.Config.Tty && cli.isTerminalOut {
+		height, width := cli.getTtySize()
+		// To handle the case where a user repeatedly attaches/detaches without resizing their
+		// terminal, the only way to get the shell prompt to display for attaches 2+ is to artifically
+		// resize it, then go back to normal. Without this, every attach after the first will
+		// require the user to manually resize or hit enter.
+		cli.resizeTtyTo(cmd.Arg(0), height+1, width+1, false)
+
+		// After the above resizing occurs, the call to monitorTtySize below will handle resetting back
+		// to the actual size.
+		if err := cli.monitorTtySize(cmd.Arg(0), false); err != nil {
+			logrus.Debugf("Error monitoring TTY size: %s", err)
+		}
+	}
+
 	if err := cli.holdHijackedConnection(c.Config.Tty, in, cli.out, cli.err, resp); err != nil {
 		return err
 	}

api/client/utils.go

@@ -49,6 +49,10 @@ func (cli *DockerCli) registryAuthenticationPrivilegedFunc(index *registrytypes.
 
 func (cli *DockerCli) resizeTty(id string, isExec bool) {
 	height, width := cli.getTtySize()
+	cli.resizeTtyTo(id, height, width, isExec)
+}
+
+func (cli *DockerCli) resizeTtyTo(id string, height, width int, isExec bool) {
 	if height == 0 && width == 0 {
 		return
 	}