Automatically find repo root in cargo unstable-api.

Author: m-ou-se

tools/unstable-api/src/main.rs

@@ -1,6 +1,6 @@
 use std::{env, path::PathBuf};
 
-use anyhow::Error;
+use anyhow::{Context, Error};
 use structopt::StructOpt;
 
 mod util;
@@ -14,33 +14,23 @@ mod visit;
 struct Opt {
     /// Repository root of `rust-lang/rust`.
     #[structopt(long, parse(from_os_str))]
-    repo_root: PathBuf,
+    repo_root: Option<PathBuf>,
     #[structopt(long)]
     feature: String,
 }
 
 fn main() -> Result<(), Error> {
     let opt = Opt::from_iter(env::args().filter(|arg| arg != "unstable-api"));
 
+    let repo_root = match opt.repo_root {
+        Some(p) => p,
+        None => find_repo_root()?,
+    };
+
     let libs = vec![
-        {
-            let mut lib_core = opt.repo_root.clone();
-            lib_core.push("library");
-            lib_core.push("core");
-            lib_core
-        },
-        {
-            let mut lib_alloc = opt.repo_root.clone();
-            lib_alloc.push("library");
-            lib_alloc.push("alloc");
-            lib_alloc
-        },
-        {
-            let mut lib_std = opt.repo_root.clone();
-            lib_std.push("library");
-            lib_std.push("std");
-            lib_std
-        },
+        repo_root.clone().join("library/core"),
+        repo_root.clone().join("library/alloc"),
+        repo_root.clone().join("library/std"),
     ];
 
     for crate_root in libs {
@@ -49,3 +39,16 @@ fn main() -> Result<(), Error> {
 
     Ok(())
 }
+
+fn find_repo_root() -> Result<PathBuf, Error> {
+    let path = std::process::Command::new("cargo")
+        .arg("locate-project")
+        .arg("--workspace")
+        .arg("--message-format=plain")
+        .output()
+        .context("unable to find repository root")?
+        .stdout;
+    let mut path = PathBuf::from(String::from_utf8(path)?);
+    path.pop();
+    Ok(path)
+}