test(cli): snapshot test for -Z help

tests/testsuite/cargo/mod.rs

@@ -1 +1,2 @@
 mod help;
+mod z_help;

tests/testsuite/cargo/z_help/mod.rs

@@ -0,0 +1,13 @@
+use cargo_test_support::curr_dir;
+use cargo_test_support::prelude::*;
+
+#[cargo_test]
+fn case() {
+    snapbox::cmd::Command::cargo_ui()
+        .masquerade_as_nightly_cargo(&["-Z help"])
+        .args(["-Z", "help"])
+        .assert()
+        .success()
+        .stdout_matches_path(curr_dir!().join("stdout.log"))
+        .stderr_matches_path(curr_dir!().join("stderr.log"));
+}

tests/testsuite/cargo/z_help/stdout.log

@@ -0,0 +1,37 @@
+
+Available unstable (nightly-only) flags:
+
+    -Z allow-features          -- Allow *only* the listed unstable features
+    -Z asymmetric-token        -- Allows authenticating with asymmetric tokens
+    -Z avoid-dev-deps          -- Avoid installing dev-dependencies if possible
+    -Z binary-dep-depinfo      -- Track changes to dependency artifacts
+    -Z bindeps                 -- Allow Cargo packages to depend on bin, cdylib, and staticlib crates, and use the artifacts built by those crates
+    -Z build-std               -- Enable Cargo to compile the standard library itself as part of a crate graph compilation
+    -Z build-std-features      -- Configure features enabled for the standard library itself when building the standard library
+    -Z check-cfg               -- Enable compile-time checking of `cfg` names/values/features
+    -Z codegen-backend         -- Enable the `codegen-backend` option in profiles in .cargo/config.toml file
+    -Z config-include          -- Enable the `include` key in config files
+    -Z direct-minimal-versions -- Resolve minimal dependency versions instead of maximum (direct dependencies only)
+    -Z doctest-xcompile        -- Compile and run doctests for non-host target using runner config
+    -Z dual-proc-macros        -- Build proc-macros for both the host and the target
+    -Z gc                      -- Track cache usage and "garbage collect" unused files
+    -Z gitoxide                -- Use gitoxide for the given git interactions, or all of them if no argument is given
+    -Z host-config             -- Enable the [host] section in the .cargo/config.toml file
+    -Z lints                   -- Pass `[lints]` to the linting tools
+    -Z minimal-versions        -- Resolve minimal dependency versions instead of maximum
+    -Z msrv-policy             -- Enable rust-version aware policy within cargo
+    -Z mtime-on-use            -- Configure Cargo to update the mtime of used files
+    -Z no-index-update         -- Do not update the registry index even if the cache is outdated
+    -Z panic-abort-tests       -- Enable support to run tests with -Cpanic=abort
+    -Z profile-rustflags       -- Enable the `rustflags` option in profiles in .cargo/config.toml file
+    -Z publish-timeout         -- Enable the `publish.timeout` key in .cargo/config.toml file
+    -Z rustdoc-map             -- Allow passing external documentation mappings to rustdoc
+    -Z rustdoc-scrape-examples -- Allows Rustdoc to scrape code examples from reverse-dependencies
+    -Z script                  -- Enable support for single-file, `.rs` packages
+    -Z target-applies-to-host  -- Enable the `target-applies-to-host` key in the .cargo/config.toml file
+    -Z trim-paths              -- Enable the `trim-paths` option in profiles
+    -Z unstable-options        -- Allow the usage of unstable options
+
+Run with 'cargo -Z [FLAG] [COMMAND]'
+
+See https://doc.rust-lang.org/nightly/cargo/reference/unstable.html for more information about these flags.

tests/testsuite/help.rs

@@ -43,17 +43,6 @@ fn help_external_subcommand() {
         .run();
 }
 
-#[cargo_test]
-fn z_flags_help() {
-    // Test that the output of `cargo -Z help` shows a different help screen with
-    // all the `-Z` flags.
-    cargo_process("-Z help")
-        .with_stdout_contains(
-            "    -Z allow-features[..]-- Allow *only* the listed unstable features",
-        )
-        .run();
-}
-
 fn help_with_man(display_command: &str) {
     // Build a "man" process that just echoes the contents.
     let p = project()