Add progress tracker and message for CLI while cloning a template

config/spotbugs/filter.xml

@@ -188,4 +188,10 @@
         <Bug pattern="SF_SWITCH_FALLTHROUGH"/>
     </Match>
 
+    <!-- It is not worth catching if the closing task of a progress bar fails to execute -->
+    <Match>
+        <Class name="software.amazon.smithy.cli.ProgressTracker"/>
+        <Bug pattern="DE_MIGHT_IGNORE"/>
+    </Match>
+
 </FindBugsFilter>

smithy-cli/src/main/java/software/amazon/smithy/cli/ProgressStyle.java

@@ -0,0 +1,56 @@
+/*
+ * Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+package software.amazon.smithy.cli;
+
+import software.amazon.smithy.utils.StringUtils;
+
+
+public interface ProgressStyle {
+
+    void updateAction(Command.Env env);
+
+    void closeAction(Command.Env env);
+
+    static ColorBuffer getBuffer(Command.Env env) {
+        return ColorBuffer.of(env.colors(), env.stdout());
+    }
+
+    static ProgressStyle dots(String progressMessage, String closeMessage) {
+        return new ProgressStyle() {
+            private static final String PROGRESS_CHAR = ".";
+            private static final int TICKER_LENGTH = 3;
+
+            private int totalTicks = 0;
+            private final long startTimeMillis = System.currentTimeMillis();
+
+            @Override
+            public void updateAction(Command.Env env) {
+                int tickNumber = totalTicks % (TICKER_LENGTH + 1);
+                String loadStr = StringUtils.repeat(PROGRESS_CHAR, tickNumber)
+                        + StringUtils.repeat(" ", TICKER_LENGTH - tickNumber);
+                try (ColorBuffer buffer = getBuffer(env)) {
+                    buffer.print("\r")
+                            .print(progressMessage, ColorTheme.NOTE)
+                            .print(loadStr, ColorTheme.NOTE);
+                }
+                totalTicks += 1;
+            }
+
+            @Override
+            public void closeAction(Command.Env env) {
+                try (ColorBuffer buffer = getBuffer(env)) {
+                    buffer.print("\r")
+                            .print(closeMessage, ColorTheme.SUCCESS)
+                            .print(" [", ColorTheme.MUTED)
+                            .print((System.currentTimeMillis() - startTimeMillis) / 1000.0 + "s",
+                                    ColorTheme.NOTE)
+                            .print("]", ColorTheme.MUTED)
+                            .println();
+                }
+            }
+        };
+    }
+}

smithy-cli/src/main/java/software/amazon/smithy/cli/ProgressTracker.java

@@ -0,0 +1,59 @@
+/*
+ * Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+package software.amazon.smithy.cli;
+
+import java.util.concurrent.ExecutionException;
+import java.util.concurrent.Executors;
+import java.util.concurrent.ScheduledFuture;
+import java.util.concurrent.ScheduledThreadPoolExecutor;
+import java.util.concurrent.TimeUnit;
+
+public final class ProgressTracker implements AutoCloseable {
+    private static final ScheduledThreadPoolExecutor EXECUTOR = new ScheduledThreadPoolExecutor(1, runnable -> {
+        Thread thread = Executors.defaultThreadFactory().newThread(runnable);
+        thread.setDaemon(true);
+        return thread;
+    });
+    private static final long INTERVAL_MILLIS = 400L;
+    private final ScheduledFuture<?> task;
+    private final ProgressStyle style;
+    private final Command.Env env;
+    private final boolean quiet;
+
+    public ProgressTracker(Command.Env env, ProgressStyle style, boolean quiet) {
+        this.env = env;
+        this.style = style;
+        this.quiet = quiet;
+        // Do not print a progress bar if the quiet setting is enabled
+        if (quiet) {
+            task = null;
+        } else {
+            task = EXECUTOR.scheduleAtFixedRate(this::write, 0, INTERVAL_MILLIS, TimeUnit.MILLISECONDS);
+        }
+    }
+
+    @Override
+    public void close() {
+        if (!quiet) {
+            task.cancel(false);
+            try {
+                EXECUTOR.schedule(this::executeClose, 0, TimeUnit.NANOSECONDS).get();
+            } catch (ExecutionException | InterruptedException e) { /* ignored */ }
+        }
+    }
+
+    private void write() {
+        style.updateAction(env);
+        // Flush so the output is written immediately
+        env.stdout().flush();
+    }
+
+    private void executeClose() {
+        style.closeAction(env);
+        // Flush so the output is written immediately
+        env.stdout().flush();
+    }
+}

smithy-cli/src/main/java/software/amazon/smithy/cli/commands/InitCommand.java

@@ -35,6 +35,8 @@
 import software.amazon.smithy.cli.ColorTheme;
 import software.amazon.smithy.cli.Command;
 import software.amazon.smithy.cli.HelpPrinter;
+import software.amazon.smithy.cli.ProgressStyle;
+import software.amazon.smithy.cli.ProgressTracker;
 import software.amazon.smithy.cli.StandardOptions;
 import software.amazon.smithy.model.node.Node;
 import software.amazon.smithy.model.node.ObjectNode;
@@ -188,13 +190,18 @@ private void cloneTemplate(Path temp, ObjectNode smithyTemplatesNode, Options op
         final String templatePath = getTemplatePath(templateNode, template);
         List<String> includedFiles = getIncludedFiles(templateNode);
 
-        // Specify the subdirectory to download
-        exec(ListUtils.of("git", "sparse-checkout", "set", "--no-cone", templatePath), temp);
-        // add any additional files that should be included
-        for (String includedFile : includedFiles) {
-            exec(ListUtils.of("git", "sparse-checkout", "add", "--no-cone", includedFile), temp);
+        try (ProgressTracker t = new ProgressTracker(env,
+                ProgressStyle.dots("cloning template", "template cloned"),
+                standardOptions.quiet()
+        )) {
+            // Specify the subdirectory to download
+            exec(ListUtils.of("git", "sparse-checkout", "set", "--no-cone", templatePath), temp);
+            // add any additional files that should be included
+            for (String includedFile : includedFiles) {
+                exec(ListUtils.of("git", "sparse-checkout", "add", "--no-cone", includedFile), temp);
+            }
+            exec(ListUtils.of("git", "checkout"), temp);
         }
-        exec(ListUtils.of("git", "checkout"), temp);