If a commit is missing, dump the job. If the commit fails to merge, reportt the error

ofborg/src/checkout.rs

@@ -105,6 +105,21 @@ impl CachedProjectCo {
         }
     }
 
+    pub fn commit_exists(&self, commit: &OsStr) -> bool {
+        let mut lock = self.lock().expect("Failed to lock");
+
+        let result = Command::new("git")
+            .arg("show")
+            .arg(commit)
+            .current_dir(self.clone_to())
+            .status()
+            .expect("git show <commit> failed");
+
+        lock.unlock();
+
+        return result.success();
+    }
+
     pub fn merge_commit(&self, commit: &OsStr) -> Result<(), Error> {
         let mut lock = self.lock()?;
 

ofborg/src/message/buildjob.rs

@@ -20,6 +20,40 @@ pub struct Actions {
 }
 
 impl Actions {
+    pub fn commit_missing(&mut self, _job: &BuildJob) -> worker::Actions {
+        return vec![
+            worker::Action::Ack
+        ];
+    }
+
+    pub fn merge_failed(&mut self, job: &BuildJob) -> worker::Actions {
+        let msg = buildresult::BuildResult {
+            repo: job.repo.clone(),
+            pr: job.pr.clone(),
+            system: self.system.clone(),
+            output: vec![String::from("Merge failed")],
+            success: false
+        };
+
+        let props =  protocol::basic::BasicProperties {
+            content_type: Some("application/json".to_owned()),
+            ..Default::default()
+        };
+
+
+        return vec![
+            worker::Action::Publish(worker::QueueMsg{
+                exchange: Some("build-results".to_owned()),
+                routing_key: None,
+                mandatory: true,
+                immediate: false,
+                properties: Some(props),
+                content: serde_json::to_string(&msg).unwrap().into_bytes()
+            }),
+            worker::Action::Ack
+        ];
+    }
+
     pub fn build_finished(&mut self, job: &BuildJob, success: bool, lines: Vec<String>) -> worker::Actions {
         let msg = buildresult::BuildResult {
             repo: job.repo.clone(),

ofborg/src/tasks/build.rs

@@ -64,7 +64,16 @@ impl worker::SimpleWorker for BuildWorker {
 
         let refpath = co.checkout_ref(target_branch.as_ref()).unwrap();
         co.fetch_pr(job.pr.number).unwrap();
-        co.merge_commit(job.pr.head_sha.as_ref()).unwrap();
+
+        if !co.commit_exists(job.pr.head_sha.as_ref()) {
+            info!("Commit {} doesn't exist", job.pr.head_sha);
+            return self.actions().commit_missing(&job);
+        }
+
+        if let Err(_) = co.merge_commit(job.pr.head_sha.as_ref()) {
+            info!("Failed to merge {}", job.pr.head_sha);
+            return self.actions().merge_failed(&job);
+        }
 
         println!("Got path: {:?}, building", refpath);