Rewrap PR bodies and custom squash messages to 72 characters

Cargo.toml

@@ -66,6 +66,7 @@ tempfile = "3"
 which = "8"
 
 # Text processing
+comrak = { version = "0.50.0", default-features = false }
 pulldown-cmark = "0.13"
 regex = "1"
 

src/bors/handlers/squash.rs

@@ -3,7 +3,9 @@ use crate::bors::gitops_queue::{
     GitOpsCommand, GitOpsQueueSender, PullRequestId, PushCallback, PushCommand,
 };
 use crate::bors::handlers::{PullRequestData, unapprove_pr};
-use crate::bors::{CommandPrefix, Comment, RepositoryState, bors_commit_author};
+use crate::bors::{
+    CommandPrefix, Comment, RepositoryState, bors_commit_author, format_commit_message,
+};
 use crate::database::BuildStatus;
 use crate::github::api::CommitAuthor;
 use crate::github::api::operations::Commit;
@@ -117,8 +119,10 @@ pub(super) async fn command_squash(
     // Create the squashed commit on the source repository.
     // We take the parents of the first commit, and the tree of the last commit, to create the
     // squashed commit.
-    let commit_msg =
-        commit_message.unwrap_or_else(|| generate_squashed_commit_msg(&pr.github.title, &commits));
+    let commit_msg = match commit_message {
+        Some(msg) => format_commit_message(&msg),
+        None => generate_squashed_commit_msg(&pr.github.title, &commits),
+    };
     let commit = match repo_state
         .client
         .create_commit(
@@ -528,6 +532,34 @@ mod tests {
         .await;
     }
 
+    #[sqlx::test]
+    async fn squash_long_message(pool: sqlx::PgPool) {
+        run_test((pool, squash_state()), async |ctx: &mut BorsTester| {
+            ctx.modify_pr_in_gh((), |pr| {
+                pr.add_commits(vec![Commit::from_sha("sha2")]);
+            });
+            ctx.approve(()).await?;
+            ctx.post_comment(
+                "@bors squash msg=\"This is a squashed commit.\n\nLorem ipsum dolor sit amet, \
+                consectetur adipiscing elit, sed do eiusmod tempor incididunt ut labore et \
+                dolore\"",
+            )
+            .await?;
+            ctx.run_gitop_queue().await?;
+            ctx.expect_comments((), 1).await;
+            insta::assert_snapshot!(
+                ctx.pr(()).await.get_gh_pr().head_branch_copy().get_commit().message(),
+                @"This is a squashed commit
+
+                Lorem ipsum dolor sit amet,
+                "
+            );
+
+            Ok(())
+        })
+        .await;
+    }
+
     fn squash_state() -> GitHub {
         let gh = GitHub::default();
         let pr_author = User::default_pr_author();

src/bors/merge_queue.rs

@@ -1667,6 +1667,48 @@ also include this pls"
         .await;
     }
 
+    #[sqlx::test]
+    async fn commit_message_reflow(pool: sqlx::PgPool) {
+        run_test(pool, async |ctx: &mut BorsTester| {
+            ctx.edit_pr((), |pr| {
+                pr.description = "This is a very good PR, but it has a rather long description.
+
+Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod tempor incididunt ut \
+labore et dolore magna aliqua. Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris \
+nisi ut aliquip ex ea commodo consequat.
+
+Duis aute irure dolor in reprehenderit in voluptate velit esse cillum dolore eu fugiat nulla \
+pariatur. Excepteur sint occaecat cupidatat non proident, sunt in culpa qui officia deserunt \
+mollit anim id est laborum.
+"
+                .to_string();
+            })
+            .await?;
+
+            ctx.approve(()).await?;
+            ctx.start_and_finish_auto_build(()).await?;
+
+            insta::assert_snapshot!(ctx.auto_branch().get_commit().message(), @"
+            Auto merge of #1 - default-user:pr/1, r=default-user
+
+            Title of PR 1
+
+            This is a very good PR, but it has a rather long description.
+
+            Lorem ipsum dolor sit amet, consectetur adipiscing elit, sed do eiusmod
+            tempor incididunt ut labore et dolore magna aliqua. Ut enim ad minim
+            veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea
+            commodo consequat.
+
+            Duis aute irure dolor in reprehenderit in voluptate velit esse cillum
+            dolore eu fugiat nulla pariatur. Excepteur sint occaecat cupidatat non
+            proident, sunt in culpa qui officia deserunt mollit anim id est laborum.
+            ");
+            Ok(())
+        })
+        .await;
+    }
+
     #[sqlx::test]
     async fn cancel_try_again(pool: sqlx::PgPool) {
         run_test(pool, async |ctx: &mut BorsTester| {

src/bors/mod.rs

@@ -316,7 +316,7 @@ pub fn make_text_ignored_by_bors(text: &str) -> String {
     format!("{IGNORE_BLOCK_START}\n{text}\n{IGNORE_BLOCK_END}")
 }
 
-/// Remove homu-ignore blocks from the merge message
+/// Remove homu-ignore blocks from the merge message, then rewrap the text.
 pub fn normalize_merge_message(message: &str) -> String {
     static IGNORE_REGEX: LazyLock<Regex> = LazyLock::new(|| {
         RegexBuilder::new(r"<!--\s*homu-ignore:start\s*-->.*?<!--\s*homu-ignore:end\s*-->")
@@ -326,7 +326,22 @@ pub fn normalize_merge_message(message: &str) -> String {
             .build()
             .unwrap()
     });
-    IGNORE_REGEX.replace_all(message, "").to_string()
+    let cleaned = IGNORE_REGEX.replace_all(message, "");
+    format_commit_message(&cleaned)
+}
+
+/// Rewrap PR bodies to standard commit message width.
+pub fn format_commit_message(message: &str) -> String {
+    let mut opts = comrak::Options::default();
+    opts.render.width = 72;
+    opts.render.list_style = comrak::options::ListStyleType::Star;
+
+    let mut out = String::new();
+    let arena = comrak::Arena::new();
+    let node = comrak::parse_document(&arena, message, &opts);
+    comrak::format_commonmark(&node, &opts, &mut out).unwrap();
+
+    out
 }
 
 pub fn create_merge_commit_message(pr: handlers::PullRequestData, merge_type: MergeType) -> String {