1 files changed, 35 insertions, 0 deletions
diff --git a/src/bootstrap/bin/main.rs b/src/bootstrap/bin/main.rs
index b67486c9628..f7512aa9fce 100644
--- a/src/bootstrap/bin/main.rs
+++ b/src/bootstrap/bin/main.rs
@@ -12,5 +12,40 @@ use bootstrap::{Build, Config};
 fn main() {
     let args = env::args().skip(1).collect::<Vec<_>>();
     let config = Config::parse(&args);
+
+    let changelog_suggestion = check_version(&config);
+    if let Some(suggestion) = &changelog_suggestion {
+        println!("{}", suggestion);
+    }
+
     Build::new(config).build();
+
+    if let Some(suggestion) = changelog_suggestion {
+        println!("{}", suggestion);
+        println!("note: this message was printed twice to make it more likely to be seen");
+    }
+}
+
+fn check_version(config: &Config) -> Option<String> {
+    const VERSION: usize = 1;
+
+    let mut msg = String::new();
+
+    let suggestion = if let Some(seen) = config.changelog_seen {
+        if seen != VERSION {
+            msg.push_str("warning: there have been changes to x.py since you last updated.\n");
+            format!("update `config.toml` to use `changelog-seen = {}` instead", VERSION)
+        } else {
+            return None;
+        }
+    } else {
+        msg.push_str("warning: x.py has made several changes recently you may want to look at\n");
+        format!("add `changelog-seen = {}` to `config.toml`", VERSION)
+    };
+
+    msg.push_str("help: consider looking at the changes in `src/bootstrap/CHANGELOG.md`\n");
+    msg.push_str("note: to silence this warning, ");
+    msg.push_str(&suggestion);
+
+    Some(msg)
 }