Allow setting squashed commit message to the PR body

src/bors/command/mod.rs

@@ -100,6 +100,16 @@ pub struct DelegateCommand {
     pub permission: DelegatedPermission,
 }
 
+#[derive(Debug, PartialEq)]
+pub enum SquashCommitMessage {
+    /// Automatically generate a commit message based on the messages of the squashed commits.
+    AutoGenerate,
+    /// Set the commit message to the PR body.
+    PullRequestDescription,
+    /// Set an explicit commit message.
+    Explicit(String),
+}
+
 /// Bors command specified by a user.
 ///
 /// When modifying commands, remember to also update:
@@ -162,5 +172,5 @@ pub enum BorsCommand {
     /// Cancel an auto build currently running on a given PR (without removing it from the queue).
     Cancel,
     /// Squash all commits of a pull request into a single commit.
-    Squash { commit_message: Option<String> },
+    Squash { commit_message: SquashCommitMessage },
 }

src/bors/command/parser.rs

@@ -1,7 +1,7 @@
 //! Defines parsers for bors commands.
 
 use crate::bors::command::{
-    Approver, BorsCommand, CommandPrefix, DelegateCommand, Delegatee, Parent,
+    Approver, BorsCommand, CommandPrefix, DelegateCommand, Delegatee, Parent, SquashCommitMessage,
 };
 use crate::database::DelegatedPermission;
 use crate::github::CommitSha;
@@ -630,20 +630,28 @@ fn parser_squash(command: &CommandPart<'_>, parts: &[CommandPart<'_>]) -> ParseR
     match command {
         CommandPart::Bare("squash") => match parts {
             &[] => Some(Ok(BorsCommand::Squash {
-                commit_message: None,
+                commit_message: SquashCommitMessage::AutoGenerate,
             })),
             &[
                 CommandPart::KeyValue {
                     key: "msg" | "message",
                     value,
                 },
                 ..,
-            ] => Some(Ok(BorsCommand::Squash {
-                commit_message: Some(value.to_owned()),
-            })),
+            ] => {
+                if value == "description" {
+                    Some(Ok(BorsCommand::Squash {
+                        commit_message: SquashCommitMessage::PullRequestDescription,
+                    }))
+                } else {
+                    Some(Ok(BorsCommand::Squash {
+                        commit_message: SquashCommitMessage::Explicit(value.to_owned()),
+                    }))
+                }
+            }
             [part, ..] => Some(Err(CommandParseError::UnknownArg {
                 arg: part.as_key().to_owned(),
-                did_you_mean: "squash [msg|message=\"<commit-msg>\"]".to_string(),
+                did_you_mean: "squash [msg|message=\"<commit-msg>\"|description]".to_string(),
             })),
         },
         _ => None,
@@ -1896,13 +1904,15 @@ for the crater",
     #[test]
     fn parse_squash() {
         let cmds = parse_commands("@bors squash");
-        assert_eq!(cmds.len(), 1);
-        assert_eq!(
-            cmds[0],
-            Ok(BorsCommand::Squash {
-                commit_message: None
-            })
-        );
+        insta::assert_debug_snapshot!(cmds, @"
+        [
+            Ok(
+                Squash {
+                    commit_message: AutoGenerate,
+                },
+            ),
+        ]
+        ");
     }
 
     #[test]
@@ -1912,7 +1922,7 @@ for the crater",
         [
             Ok(
                 Squash {
-                    commit_message: Some(
+                    commit_message: Explicit(
                         "foo",
                     ),
                 },
@@ -1928,7 +1938,7 @@ for the crater",
         [
             Ok(
                 Squash {
-                    commit_message: Some(
+                    commit_message: Explicit(
                         "foo",
                     ),
                 },
@@ -1944,7 +1954,7 @@ for the crater",
         [
             Ok(
                 Squash {
-                    commit_message: Some(
+                    commit_message: Explicit(
                         "foo bar baz",
                     ),
                 },
@@ -1953,6 +1963,20 @@ for the crater",
         "#);
     }
 
+    #[test]
+    fn parse_squash_msg_description() {
+        let cmds = parse_commands("@bors squash msg=description");
+        insta::assert_debug_snapshot!(cmds, @"
+        [
+            Ok(
+                Squash {
+                    commit_message: PullRequestDescription,
+                },
+            ),
+        ]
+        ");
+    }
+
     #[test]
     fn parse_squash_unknown_arg() {
         let cmds = parse_commands("@bors squash commit=foo");
@@ -1961,7 +1985,7 @@ for the crater",
             Err(
                 UnknownArg {
                     arg: "commit",
-                    did_you_mean: "squash [msg|message=\"<commit-msg>\"]",
+                    did_you_mean: "squash [msg|message=\"<commit-msg>\"|description]",
                 },
             ),
         ]
@@ -1975,7 +1999,7 @@ for the crater",
         [
             Ok(
                 Squash {
-                    commit_message: Some(
+                    commit_message: Explicit(
                         "foo",
                     ),
                 },

src/bors/handlers/help.rs

@@ -61,8 +61,9 @@ mod tests {
             - `try cancel`: Cancel a running try build on the current PR.
             - `retry`: Clear a failed auto build status from an approved PR. This will cause the merge queue to eventually attempt to merge the PR again.
             - `cancel` | `yield`: Cancel a running auto build on the current PR.
-            - `squash [msg|message=<commit-message>]`: Squash the commits of a PR into a single commit.
+            - `squash [msg|message=<commit-message>|description]`: Squash the commits of a PR into a single commit.
                 - Optionally, you can specify a `<commit-message>` for the created commit. If not specified, the commit messages of all squashed commits will be combined.
+                - If you specify `msg=description`, then the PR body will be used as the squashed commit message.
             - `info`: Get information about the current PR
 
             ## Repository management

src/bors/handlers/squash.rs

@@ -1,4 +1,5 @@
 use crate::PgDbClient;
+use crate::bors::command::SquashCommitMessage;
 use crate::bors::comment::CommentTag;
 use crate::bors::gitops_queue::{
     GitOpsCommand, GitOpsQueueSender, PullRequestId, PushCallback, PushCommand,
@@ -27,7 +28,7 @@ pub(super) async fn command_squash(
     db: Arc<PgDbClient>,
     pr: PullRequestData<'_>,
     author: &GithubUser,
-    commit_message: Option<String>,
+    commit_message: SquashCommitMessage,
     bot_prefix: &CommandPrefix,
     gitops_queue: &GitOpsQueueSender,
 ) -> anyhow::Result<()> {
@@ -142,8 +143,13 @@ 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 {
+        SquashCommitMessage::AutoGenerate => {
+            generate_squashed_commit_msg(&pr.github.title, &commits)
+        }
+        SquashCommitMessage::PullRequestDescription => pr.github.message.clone(),
+        SquashCommitMessage::Explicit(msg) => msg,
+    };
     let commit_msg = add_coauthored_authors(commit_msg, &commits, &commit_author);
     let commit = match repo_state
         .client

src/bors/mod.rs

@@ -127,8 +127,9 @@ You can use the following commands:
 - `try cancel`: Cancel a running try build on the current PR.
 - `retry`: Clear a failed auto build status from an approved PR. This will cause the merge queue to eventually attempt to merge the PR again.
 - `cancel` | `yield`: Cancel a running auto build on the current PR.
-- `squash [msg|message=<commit-message>]`: Squash the commits of a PR into a single commit.
+- `squash [msg|message=<commit-message>|description]`: Squash the commits of a PR into a single commit.
     - Optionally, you can specify a `<commit-message>` for the created commit. If not specified, the commit messages of all squashed commits will be combined.
+    - If you specify `msg=description`, then the PR body will be used as the squashed commit message.
 - `info`: Get information about the current PR
 
 ## Repository management