Better suggestion for unsupported -path flag

Signed-off-by: hi-rustin <rustin.liu@gmail.com>

src/bin/cargo/commands/add.rs

@@ -77,7 +77,7 @@ Example uses:
                 "Ignore `rust-version` specification in packages (unstable)"
             ),
         ])
-        .arg_manifest_path()
+        .arg_manifest_path_without_unsupported_path_tip()
         .arg_package("Package to modify")
         .arg_dry_run("Don't actually write the manifest")
         .arg_quiet()

src/cargo/util/command_prelude.rs

@@ -267,6 +267,20 @@ pub trait CommandExt: Sized {
     }
 
     fn arg_manifest_path(self) -> Self {
+        // We use `--manifest-path` instead of `--path`.
+        let unsupported_path_arg = {
+            let value_parser = UnknownArgumentValueParser::suggest_arg("--manifest-path");
+            flag("unsupported-path-flag", "")
+                .long("path")
+                .value_parser(value_parser)
+                .hide(true)
+        };
+        self.arg_manifest_path_without_unsupported_path_tip()
+            ._arg(unsupported_path_arg)
+    }
+
+    // `cargo add` has a `--path` flag to install a crate from a local path.
+    fn arg_manifest_path_without_unsupported_path_tip(self) -> Self {
         self._arg(
             opt("manifest-path", "Path to Cargo.toml")
                 .value_name("PATH")

tests/testsuite/build.rs

@@ -218,6 +218,8 @@ fn cargo_compile_with_wrong_manifest_path_flag() {
             "\
 error: unexpected argument '--path' found
 
+  tip: a similar argument exists: '--manifest-path'
+
 Usage: cargo[EXE] build [OPTIONS]
 
 For more information, try '--help'.