[antlir2][image_test] move help to subcommand

Summary:
For more dynamic (in other words, useful) help, move it into the Rust binary.
This doesn't actually make the help more helpful, but opens the door to do so.

Test Plan:
```
❯ buck2 run fbcode//antlir/antlir2/testing/tests:test-rust-boot-centos9[container]
2dae0e08-92fc-404d-a1e1-1516d437dfc6 login: root (automatic login)

┏━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━┓
┃                                                                                    ┃
┃  This is an antlir2 booted image test.                                             ┃
┃                                                                                    ┃
┃  Press ^] three times within 1s to kill the container.                             ┃
┃                                                                                    ┃
┃  You have been auto-logged in to a root console. Feel free to mess around here,    ┃
┃  any changes you make will be thrown away when the container exits.                ┃
┃                                                                                    ┃
┃  Soon, this will be populated with a copy-pasteable command, but for now...        ┃
┃                                                                                    ┃
┃  To run your test interactively:                                                   ┃
┃                                                                                    ┃
┃  In another shell on your host:                                                    ┃
┃                                                                                    ┃
┃  'buck2 build --show-full-output $test[inner_test]'                                ┃
┃                                                                                    ┃
┃  In this shell:                                                                    ┃
┃                                                                                    ┃
┃  Run the binary at that path printed above                                         ┃
┃  EOF                                                                               ┃
┃                                                                                    ┃
┗━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━┛
  ╲
   ╲   \_\_    _/_/
    ╲      \__/
           (oo)\_______
           (__)\       )\/\
               ||----w |
               ||     ||

[root@2dae0e08-92fc-404d-a1e1-1516d437dfc6 ~]#
```

Reviewed By: epilatow

Differential Revision: D65823556

fbshipit-source-id: 0d8f938b3c9c79f595114f6d76025802c2d83ff4

antlir/antlir2/testing/image_test/BUCK

@@ -24,6 +24,7 @@ rust_binary(
         "clap",
         "serde",
         "tempfile",
+        "textwrap",
         "tracing",
         "tracing-subscriber",
         ":image_test_lib",
@@ -55,6 +56,11 @@ feature.new(
             dst = "/etc/profile.d/zz-help.sh",
             mode = "a+rx",
         ),
+        feature.ensure_dirs_exist(dirs = "/__antlir2_image_test__"),
+        feature.install(
+            src = ":image-test",
+            dst = "/__antlir2_image_test__/image-test",
+        ),
     ],
     visibility = ["PUBLIC"],
 )

antlir/antlir2/testing/image_test/help.sh

@@ -4,55 +4,4 @@
 # This source code is licensed under the MIT license found in the
 # LICENSE file in the root directory of this source tree.
 
-# Generated with:
-#
-# cowsay -f moose -W 80 <<EOF
-# This is an antlir2 booted image test.
-#
-# Press ^] three times within 1s to kill the container.
-#
-# You have been auto-logged in to a root console. Feel free to mess around here,
-# any changes you make will be thrown away when the container exits.
-#
-# Soon, this will be populated with a copy-pasteable command, but for now...
-#
-# To run your test interactively:
-#
-# In another shell on your host:
-#
-# 'buck2 build --show-full-output \$test[inner_test]'
-#
-# In this shell:
-#
-# Run the binary at that path printed above
-# EOF
-
-cat <<EOF
- ________________________________________________________________________________
-/ This is an antlir2 booted image test.                                          \\
-|                                                                                |
-| Press ^] three times within 1s to kill the container.                          |
-|                                                                                |
-| You have been auto-logged in to a root console. Feel free to mess around here, |
-| any changes you make will be thrown away when the container exits.             |
-|                                                                                |
-| Soon, this will be populated with a copy-pasteable command, but for now...     |
-|                                                                                |
-| To run your test interactively:                                                |
-|                                                                                |
-| In another shell on your host:                                                 |
-|                                                                                |
-| 'buck2 build --show-full-output '\$test[inner_test]'                            |
-|                                                                                |
-| In this shell:                                                                 |
-|                                                                                |
-\ Run the binary at that path printed above                                      /
- --------------------------------------------------------------------------------
-  \\
-   \\  \_\_    _/_/
-    \\     \__/
-           (oo)\_______
-           (__)\       )\/\\
-               ||----w |
-               ||     ||
-EOF
+/__antlir2_image_test__/image-test shell-help

antlir/antlir2/testing/image_test/src/main.rs

@@ -9,6 +9,7 @@ use anyhow::Result;
 use clap::Parser;
 
 mod runtime;
+mod shell_help;
 mod spawn;
 
 pub(crate) use runtime::RuntimeSpec;
@@ -17,6 +18,7 @@ pub(crate) use runtime::RuntimeSpec;
 enum Args {
     /// Spawn a container to run the test
     Spawn(spawn::Args),
+    ShellHelp(shell_help::Args),
 }
 
 fn main() -> Result<()> {
@@ -26,5 +28,6 @@ fn main() -> Result<()> {
 
     match args {
         Args::Spawn(a) => a.run(),
+        Args::ShellHelp(a) => a.run(),
     }
 }

antlir/antlir2/testing/image_test/src/shell_help.rs

@@ -0,0 +1,81 @@
+/*
+ * Copyright (c) Meta Platforms, Inc. and affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ */
+
+use anyhow::Result;
+use clap::Parser;
+
+#[derive(Parser, Debug)]
+pub(crate) struct Args {}
+
+const MESSAGE: &str = r#"
+This is an antlir2 booted image test.
+
+Press ^] three times within 1s to kill the container.
+
+You have been auto-logged in to a root console. Feel free to mess around here,
+any changes you make will be thrown away when the container exits.
+
+Soon, this will be populated with a copy-pasteable command, but for now...
+
+To run your test interactively:
+
+In another shell on your host:
+
+'buck2 build --show-full-output $test[inner_test]'
+
+In this shell:
+
+Run the binary at that path printed above
+EOF
+"#;
+
+const WIDTH: usize = 80;
+const PADDING: usize = 2;
+
+const MOOSE: &str = r#"  ╲
+   ╲   \_\_    _/_/
+    ╲      \__/
+           (oo)\_______
+           (__)\       )\/\
+               ||----w |
+               ||     ||
+"#;
+
+impl Args {
+    pub(crate) fn run(self) -> Result<()> {
+        let wrapped = textwrap::wrap(MESSAGE, WIDTH);
+        let mut buf = String::with_capacity(MESSAGE.len() + (4 * WIDTH * wrapped.len()));
+        buf.push('┏');
+        for _ in 0..(WIDTH + PADDING * 2) {
+            buf.push('━');
+        }
+        buf.push('┓');
+        buf.push('\n');
+        for line in wrapped {
+            buf.push('┃');
+            for _ in 0..PADDING {
+                buf.push(' ');
+            }
+            buf.push_str(&line);
+            let padding = WIDTH - line.len() + PADDING;
+            for _ in 0..padding {
+                buf.push(' ');
+            }
+            buf.push('┃');
+            buf.push('\n');
+        }
+        buf.push('┗');
+        for _ in 0..(WIDTH + PADDING * 2) {
+            buf.push('━');
+        }
+        buf.push('┛');
+        buf.push('\n');
+        buf.push_str(MOOSE);
+        println!("{}", buf);
+        Ok(())
+    }
+}