Update the semver-check script to be able to run in any directory.

crates/semver-check/src/main.rs

@@ -23,9 +23,13 @@ fn main() {
 const SEPARATOR: &str = "///////////////////////////////////////////////////////////";
 
 fn doit() -> Result<(), Box<dyn Error>> {
-    let filename = std::env::args()
-        .nth(1)
-        .unwrap_or_else(|| "src/doc/src/reference/semver.md".to_string());
+    let filename = std::env::args().nth(1).unwrap_or_else(|| {
+        Path::new(env!("CARGO_MANIFEST_DIR"))
+            .join("../../src/doc/src/reference/semver.md")
+            .to_str()
+            .unwrap()
+            .to_string()
+    });
     let contents = fs::read_to_string(filename)?;
     let mut lines = contents.lines().enumerate();
 

src/doc/README.md

@@ -55,8 +55,12 @@ To rebuild the man pages, run `cargo build-man` inside the workspace.
 ### SemVer chapter tests
 
 There is a script to verify that the examples in the SemVer chapter work as
-intended. To run the tests, go into the `semver-check` directory and run
-`cargo run`.
+intended. To run the tests, run `cargo +stable run -p semver-check`.
+
+Note that these tests run on the most recent stable release because they
+validate the output of the compiler diagnostics. The output can change between
+releases, so we pin to a specific release to avoid frequent and unexpected
+breakage.
 
 ## Contributing