Enable cargo override to be run correctly as a cargo subcommand

Fixes #23

This makes it possible to run `cargo override --path ../dep` where previously `cargo-override --path ../dep` had to be used.

src/lib.rs

@@ -12,14 +12,24 @@ pub static DEFAULT_REGISTRY: &str = "crates-io";
 pub static CARGO_TOML: &str = "Cargo.toml";
 
 #[derive(Parser, Debug)]
-#[command(author, version, about, long_about = None)]
-pub struct Args {
-    #[arg(short, long)]
-    pub path: String,
+#[command(bin_name = "cargo")]
+pub struct Cli {
+    #[command(subcommand)]
+    pub command: CargoInvocation,
 }
 
-pub fn run(working_dir: &Path, args: Args) -> anyhow::Result<()> {
-    let patch_manifest_path = patch_manifest(working_dir, &args.path)?;
+#[derive(Parser, Debug)]
+pub enum CargoInvocation {
+    #[command(name = "override")]
+    Override { path: String },
+}
+
+pub fn run(working_dir: &Path, args: Cli) -> anyhow::Result<()> {
+    let Cli {
+        command: CargoInvocation::Override { path },
+    } = args;
+
+    let patch_manifest_path = patch_manifest(working_dir, &path)?;
 
     let project_manifest_path = project_manifest(working_dir)?;
 
@@ -37,7 +47,7 @@ pub fn run(working_dir: &Path, args: Args) -> anyhow::Result<()> {
     let project_patch_overrides_table =
         create_subtable(project_patch_table, DEFAULT_REGISTRY, false)?;
 
-    let Ok(new_patch) = format!("{{ path = \"{}\" }}", args.path).parse::<toml_edit::Item>() else {
+    let Ok(new_patch) = format!("{{ path = \"{}\" }}", path).parse::<toml_edit::Item>() else {
         todo!("We haven't escaped the path so we can't be sure this will parse")
     };
 

src/main.rs

@@ -1,11 +1,11 @@
 use std::env::current_dir;
 
-use cargo_override::{run, Args};
+use cargo_override::{run, Cli};
 
 use clap::Parser;
 
 fn main() {
-    let args = Args::parse();
+    let args = Cli::parse();
 
     if let Err(e) = run(&current_dir().unwrap(), args) {
         eprintln!("error: {e}");

tests/tests.rs

@@ -8,7 +8,7 @@ use std::{
     path::{Path, PathBuf},
 };
 
-use cargo_override::{run, Args, CARGO_TOML};
+use cargo_override::{run, CargoInvocation, Cli, CARGO_TOML};
 
 use fake::{Fake, Faker};
 use googletest::{
@@ -42,12 +42,7 @@ fn patch_exists() {
         &Manifest::new(Header::basic(patch_crate_name)).render(),
     );
 
-    let result = run(
-        working_dir,
-        Args {
-            path: patch_folder.to_string(),
-        },
-    );
+    let result = run(working_dir, override_path(patch_folder));
     expect_that!(result, ok(eq(())));
 
     let manifest = fs::read_to_string(working_dir_manifest_path).unwrap();
@@ -95,12 +90,7 @@ fn patch_exists_put_project_does_not_have_dep() {
         &Manifest::new(Header::basic("patch-package")).render(),
     );
 
-    let result = run(
-        working_dir,
-        Args {
-            path: patch_folder.to_string(),
-        },
-    );
+    let result = run(working_dir, override_path(patch_folder));
     expect_that!(result, err(anything()));
 }
 
@@ -128,7 +118,7 @@ fn missing_manifest() {
 
     File::create_new(patch_manifest).expect("failed to create patch manifest file");
 
-    let result = run(working_dir, Args { path: patch_folder });
+    let result = run(working_dir, override_path(patch_folder));
 
     expect_that!(
         result,
@@ -145,12 +135,7 @@ fn patch_path_doesnt_exist() {
 
     let patch_folder: String = Faker.fake();
 
-    let result = run(
-        working_dir,
-        Args {
-            path: patch_folder.clone(),
-        },
-    );
+    let result = run(working_dir, override_path(patch_folder.clone()));
 
     expect_that!(
         result,
@@ -171,12 +156,7 @@ fn patch_manifest_doesnt_exist() {
 
     fs::create_dir(patch_folder_path).expect("failed to create patch folder");
 
-    let result = run(
-        working_dir,
-        Args {
-            path: patch_folder.clone(),
-        },
-    );
+    let result = run(working_dir, override_path(patch_folder.clone()));
 
     expect_that!(
         result,
@@ -186,3 +166,9 @@ fn patch_manifest_doesnt_exist() {
         ))))
     )
 }
+
+fn override_path(path: impl Into<String>) -> Cli {
+    Cli {
+        command: CargoInvocation::Override { path: path.into() },
+    }
+}