Auto merge of rust-lang#48252 - Mark-Simulacrum:exclude-paths, r=alexcrichton

Fix not running some steps in CI

We'd previously assumed that these paths would be relative to the src
dir, and that for example our various CI scripts would, when calling
x.py, use `../x.py build ../src/tools/...` but this isn't the case --
they use `../x.py` without using the relevant source-relative path.

We eventually may want to make this (actually somewhat logical) change,
but this is not that time.

r? @kennytm

Author: bors

src/bootstrap/builder.rs

@@ -217,7 +217,7 @@ impl StepDescription {
                 }
 
                 if !attempted_run {
-                    eprintln!("Warning: no rules matched {}.", path.display());
+                    panic!("Error: no rules matched {}.", path.display());
                 }
             }
         }
@@ -385,6 +385,12 @@ impl<'a> Builder<'a> {
             Subcommand::Clean { .. } => panic!(),
         };
 
+        if let Some(path) = paths.get(0) {
+            if path == Path::new("nonexistent/path/to/trigger/cargo/metadata") {
+                return;
+            }
+        }
+
         let builder = Builder {
             build,
             top_stage: build.config.stage.unwrap_or(2),

src/bootstrap/flags.rs

@@ -278,9 +278,7 @@ Arguments:
         let src = matches.opt_str("src").map(PathBuf::from)
             .or_else(|| env::var_os("SRC").map(PathBuf::from))
             .unwrap_or(cwd.clone());
-        let paths = matches.free[1..].iter().map(|p| {
-            cwd.join(p).strip_prefix(&src).expect("paths passed to be inside checkout").into()
-        }).collect::<Vec<PathBuf>>();
+        let paths = matches.free[1..].iter().map(|p| p.into()).collect::<Vec<PathBuf>>();
 
         let cfg_file = matches.opt_str("config").map(PathBuf::from).or_else(|| {
             if fs::metadata("config.toml").is_ok() {
@@ -380,9 +378,7 @@ Arguments:
             cmd,
             incremental: matches.opt_present("incremental"),
             exclude: split(matches.opt_strs("exclude"))
-                .into_iter().map(|p| {
-                    cwd.join(p).strip_prefix(&src).expect("paths to be inside checkout").into()
-                }).collect::<Vec<_>>(),
+                .into_iter().map(|p| p.into()).collect::<Vec<_>>(),
             src,
         }
     }