add check_diff crate skeleton code

Author: benluiwj

check_diff/.gitignore

@@ -0,0 +1 @@
+/target

check_diff/Cargo.lock

@@ -0,0 +1,9 @@
+[package]
+name = "check_diff"
+version = "0.1.0"
+edition = "2021"
+
+# See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+
+[dependencies]
+clap = { version = "4.4.2", features = ["derive"] }

check_diff/Cargo.toml

@@ -0,0 +1,25 @@
+use clap::Parser;
+/// Inputs for the check_diff script
+#[derive(Parser)]
+struct CliInputs {
+    /// Git url of a rustfmt fork to compare against the latest master rustfmt
+    remote_repo_url: String,
+    /// Name of the feature branch on the forked repo
+    feature_branch: String,
+    /// Optional commit hash from the feature branch
+    #[arg(short, long)]
+    commit_hash: Option<String>,
+    /// Optional comma separated list of rustfmt config options to
+    /// pass when running the feature branch
+    #[arg(value_delimiter = ',', short, long, num_args = 1..)]
+    rustfmt_config: Option<Vec<String>>,
+}
+
+fn main() {
+    let args = CliInputs::parse();
+    println!(
+        "remote_repo_url: {:?}, feature_branch: {:?},
+        optional_commit_hash: {:?}, optional_rustfmt_config: {:?}",
+        args.remote_repo_url, args.feature_branch, args.commit_hash, args.rustfmt_config
+    );
+}

check_diff/src/main.rs

@@ -390,6 +390,14 @@ fn self_tests() {
         path.push("main.rs");
         files.push(path);
     }
+    // for crates that need to be included but lies outside src
+    let external_crates = vec!["check_diff"];
+    for external_crate in external_crates {
+        let mut path = PathBuf::from(external_crate);
+        path.push("src");
+        path.push("main.rs");
+        files.push(path);
+    }
     files.push(PathBuf::from("src/lib.rs"));
 
     let (reports, count, fails) = check_files(files, &Some(PathBuf::from("rustfmt.toml")));