Prevent spam from GitHub mentions in merge commits

Cargo.toml

@@ -54,6 +54,9 @@ chrono = "0.4"
 
 itertools = "0.14"
 
+# Text processing
+regex = "1"
+
 [dev-dependencies]
 insta = "1.26"
 wiremock = "0.6"

src/bors/handlers/trybuild.rs

@@ -20,6 +20,7 @@ use crate::github::{
     CommitSha, GithubUser, LabelTrigger, MergeError, PullRequest, PullRequestNumber,
 };
 use crate::permissions::PermissionType;
+use crate::utils::text::suppress_github_mentions;
 
 use super::deny_request;
 use super::has_permission;
@@ -286,7 +287,7 @@ fn auto_merge_commit_message(
 {pr_message}"#,
         pr_label = pr.head_label,
         pr_title = pr.title,
-        pr_message = pr.message,
+        pr_message = suppress_github_mentions(&pr.message),
         repo_owner = name.owner(),
         repo_name = name.name()
     );

src/utils/mod.rs

@@ -1,2 +1,3 @@
 pub mod logging;
+pub mod text;
 pub mod timing;

src/utils/text.rs

@@ -0,0 +1,29 @@
+use regex::{Captures, Regex};
+
+/// Replaces github @mentions with backticks to prevent accidental pings
+pub fn suppress_github_mentions(text: &str) -> String {
+    if !text.contains('@') {
+        return text.to_string();
+    }
+
+    let pattern = r"\B(@\S+)";
+
+    let re = Regex::new(pattern).unwrap();
+    re.replace_all(text, |caps: &Captures| format!("`{}`", &caps[1]))
+        .to_string()
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_suppress_github_mentions() {
+        assert_eq!(suppress_github_mentions("r? @matklad\n"), "r? `@matklad`\n");
+        assert_eq!(suppress_github_mentions("@bors r+\n"), "`@bors` r+\n");
+        assert_eq!(
+            suppress_github_mentions("[email protected]"),
+            "[email protected]"
+        )
+    }
+}