diff --git a/ofborg/src/bin/mass-rebuilder.rs b/ofborg/src/bin/mass-rebuilder.rs
index 3aabac4..06c9561 100644
--- a/ofborg/src/bin/mass-rebuilder.rs
+++ b/ofborg/src/bin/mass-rebuilder.rs
@@ -45,7 +45,7 @@ fn main() {
 
     let mrw = tasks::massrebuilder::MassRebuildWorker::new(
         cloner,
-        nix,
+        &nix,
         cfg.github(),
         cfg.acl(),
         cfg.runner.identity.clone(),
diff --git a/ofborg/src/checkout.rs b/ofborg/src/checkout.rs
index c9dd4e2..e88b351 100644
--- a/ofborg/src/checkout.rs
+++ b/ofborg/src/checkout.rs
@@ -29,7 +29,7 @@ pub struct CachedProjectCo {
 }
 
 impl CachedCloner {
-    pub fn project(&self, name: String, clone_url: String) -> CachedProject {
+    pub fn project(&self, name: &str, clone_url: String) -> CachedProject {
         // <root>/repo/<hash>/clone
         // <root>/repo/<hash>/clone.lock
         // <root>/repo/<hash>/<type>/<id>
@@ -290,7 +290,7 @@ mod tests {
         let hash = make_pr_repo(&bare.path(), &mk_co.path());
 
         let cloner = cached_cloner(&workingdir.path());
-        let project = cloner.project("commit-msg-list".to_owned(), bare.string());
+        let project = cloner.project("commit-msg-list", bare.string());
         let working_co = project
             .clone_for("testing-commit-msgs".to_owned(), "123".to_owned())
             .expect("clone should work");
@@ -317,7 +317,7 @@ mod tests {
         let hash = make_pr_repo(&bare.path(), &mk_co.path());
 
         let cloner = cached_cloner(&workingdir.path());
-        let project = cloner.project("commit-files-changed-list".to_owned(), bare.string());
+        let project = cloner.project("commit-files-changed-list", bare.string());
         let working_co = project
             .clone_for("testing-files-changed".to_owned(), "123".to_owned())
             .expect("clone should work");
diff --git a/ofborg/src/tagger.rs b/ofborg/src/tagger.rs
index dc76eee..e7289fa 100644
--- a/ofborg/src/tagger.rs
+++ b/ofborg/src/tagger.rs
@@ -77,7 +77,7 @@ impl PkgsAddedRemovedTagger {
         t
     }
 
-    pub fn changed(&mut self, removed: Vec<PackageArch>, added: Vec<PackageArch>) {
+    pub fn changed(&mut self, removed: &[PackageArch], added: &[PackageArch]) {
         if removed.len() > 0 {
             self.selected.push(String::from("8.has: clean-up"));
         }
diff --git a/ofborg/src/tasks/build.rs b/ofborg/src/tasks/build.rs
index bf52037..4c25bb5 100644
--- a/ofborg/src/tasks/build.rs
+++ b/ofborg/src/tasks/build.rs
@@ -302,7 +302,7 @@ impl notifyworker::SimpleNotifyWorker for BuildWorker {
 
         info!("Working on {}", job.pr.number);
         let project = self.cloner.project(
-            job.repo.full_name.clone(),
+            &job.repo.full_name,
             job.repo.clone_url.clone(),
         );
         let co = project
diff --git a/ofborg/src/tasks/githubcommentposter.rs b/ofborg/src/tasks/githubcommentposter.rs
index d38cf6a..6882e1d 100644
--- a/ofborg/src/tasks/githubcommentposter.rs
+++ b/ofborg/src/tasks/githubcommentposter.rs
@@ -99,7 +99,7 @@ fn result_to_check(result: &LegacyBuildResult, timestamp: DateTime<Utc>) -> Chec
 
     let mut summary: Vec<String> = vec![];
     if let Some(ref attempted) = result.attempted_attrs {
-        summary.extend(list_segment("Attempted", attempted.clone()));
+        summary.extend(list_segment("Attempted", &attempted));
     }
 
     if result.status == BuildStatus::TimedOut {
@@ -112,7 +112,7 @@ fn result_to_check(result: &LegacyBuildResult, timestamp: DateTime<Utc>) -> Chec
                 "The following builds were skipped because they don't evaluate on {}",
                 result.system
             ),
-            skipped.clone()));
+            &skipped));
     }
 
     let text: String;
@@ -193,7 +193,7 @@ fn result_to_comment(result: &LegacyBuildResult) -> String {
     reply.push("".to_owned());
 
     if let Some(ref attempted) = result.attempted_attrs {
-        reply.extend(list_segment("Attempted", attempted.clone()));
+        reply.extend(list_segment("Attempted", &attempted));
     }
 
     if let Some(ref skipped) = result.skipped_attrs {
@@ -202,7 +202,7 @@ fn result_to_comment(result: &LegacyBuildResult) -> String {
                 "The following builds were skipped because they don't evaluate on {}",
                 result.system
             ),
-            skipped.clone()));
+            &skipped));
     }
 
     if result.output.len() > 0 {
@@ -217,7 +217,7 @@ fn result_to_comment(result: &LegacyBuildResult) -> String {
     reply.join("\n")
 }
 
-fn list_segment(name: &str, things: Vec<String>) -> Vec<String> {
+fn list_segment(name: &str, things: &[String]) -> Vec<String> {
     let mut reply: Vec<String> = vec![];
 
     if things.len() > 0 {
diff --git a/ofborg/src/tasks/log_message_collector.rs b/ofborg/src/tasks/log_message_collector.rs
index 1bed597..aa63cc3 100644
--- a/ofborg/src/tasks/log_message_collector.rs
+++ b/ofborg/src/tasks/log_message_collector.rs
@@ -68,7 +68,7 @@ impl LogMessageCollector {
 
     pub fn write_metadata(&mut self, from: &LogFrom, data: &BuildLogStart) -> Result<(), String>{
         let metapath = self.path_for_metadata(&from)?;
-        let mut fp = self.open_file(metapath)?;
+        let mut fp = self.open_file(&metapath)?;
 
         match serde_json::to_string(data) {
             Ok(data) => {
@@ -87,7 +87,7 @@ impl LogMessageCollector {
 
     pub fn write_result(&mut self, from: &LogFrom, data: &BuildResult) -> Result<(), String>{
         let path = self.path_for_result(&from)?;
-        let mut fp = self.open_file(path)?;
+        let mut fp = self.open_file(&path)?;
 
         match serde_json::to_string(data) {
             Ok(data) => {
@@ -110,7 +110,7 @@ impl LogMessageCollector {
             ))
         } else {
             let logpath = self.path_for_log(&from)?;
-            let fp = self.open_file(logpath)?;
+            let fp = self.open_file(&logpath)?;
             let writer = LineWriter::new(fp);
             self.handles.insert(from.clone(), writer);
             if let Some(handle) = self.handles.get_mut(&from) {
@@ -157,7 +157,7 @@ impl LogMessageCollector {
         }
     }
 
-    fn open_file(&self, path: PathBuf) -> Result<File, String> {
+    fn open_file(&self, path: &PathBuf) -> Result<File, String> {
         let dir = path.parent().unwrap();
         fs::create_dir_all(dir).unwrap();
 
@@ -369,12 +369,12 @@ mod tests {
 
         assert!(
             worker
-                .open_file(worker.path_for_log(&make_from("a")).unwrap())
+                .open_file(&worker.path_for_log(&make_from("a")).unwrap())
                 .is_ok()
         );
         assert!(
             worker
-                .open_file(worker.path_for_log(&make_from("b.foo/123")).unwrap())
+                .open_file(&worker.path_for_log(&make_from("b.foo/123")).unwrap())
                 .is_ok()
         );
     }
diff --git a/ofborg/src/tasks/massrebuilder.rs b/ofborg/src/tasks/massrebuilder.rs
index 896be78..c4aceda 100644
--- a/ofborg/src/tasks/massrebuilder.rs
+++ b/ofborg/src/tasks/massrebuilder.rs
@@ -38,7 +38,7 @@ pub struct MassRebuildWorker<E> {
 impl<E: stats::SysEvents> MassRebuildWorker<E> {
     pub fn new(
         cloner: checkout::CachedCloner,
-        nix: nix::Nix,
+        nix: &nix::Nix,
         github: hubcaps::Github,
         acl: ACL,
         identity: String,
@@ -71,8 +71,8 @@ impl<E: stats::SysEvents> MassRebuildWorker<E> {
         if darwin {
             update_labels(
                 &issue,
-                vec![String::from("6.topic: darwin")],
-                vec![],
+                &vec![String::from("6.topic: darwin")],
+                &vec![],
             );
         }
     }
@@ -86,8 +86,8 @@ impl<E: stats::SysEvents> MassRebuildWorker<E> {
 
         update_labels(
             &issue,
-            tagger.tags_to_add(),
-            tagger.tags_to_remove(),
+            &tagger.tags_to_add(),
+            &tagger.tags_to_remove(),
         );
     }
 }
@@ -167,7 +167,7 @@ impl<E: stats::SysEvents + 'static> worker::SimpleWorker for MassRebuildWorker<E
         overall_status.set_with_description("Starting", hubcaps::statuses::State::Pending);
 
         let project = self.cloner.project(
-            job.repo.full_name.clone(),
+            &job.repo.full_name,
             job.repo.clone_url.clone(),
         );
 
@@ -211,7 +211,7 @@ impl<E: stats::SysEvents + 'static> worker::SimpleWorker for MassRebuildWorker<E
         if let Err(mut output) = rebuildsniff.find_before() {
             overall_status.set_url(make_gist(
                 &gists,
-                "Output path comparison".to_owned(),
+                "Output path comparison",
                 Some("".to_owned()),
                 file_to_str(&mut output),
             ));
@@ -251,7 +251,7 @@ impl<E: stats::SysEvents + 'static> worker::SimpleWorker for MassRebuildWorker<E
         }
 
         let possibly_touched_packages =
-            parse_commit_messages(co.commit_messages_from_head(&job.pr.head_sha).unwrap_or(
+            parse_commit_messages(&co.commit_messages_from_head(&job.pr.head_sha).unwrap_or(
                 vec!["".to_owned()],
             ));
 
@@ -272,16 +272,16 @@ impl<E: stats::SysEvents + 'static> worker::SimpleWorker for MassRebuildWorker<E
 
             update_labels(
                 &issue,
-                vec!["2.status: merge conflict".to_owned()],
-                vec![],
+                &vec!["2.status: merge conflict".to_owned()],
+                &vec![],
             );
 
             return self.actions().skip(&job);
         } else {
             update_labels(
                 &issue,
-                vec![],
-                vec!["2.status: merge conflict".to_owned()],
+                &vec![],
+                &vec!["2.status: merge conflict".to_owned()],
             );
         }
 
@@ -300,7 +300,7 @@ impl<E: stats::SysEvents + 'static> worker::SimpleWorker for MassRebuildWorker<E
         if let Err(mut output) = rebuildsniff.find_after() {
             overall_status.set_url(make_gist(
                 &gists,
-                "Output path comparison".to_owned(),
+                "Output path comparison",
                 Some("".to_owned()),
                 file_to_str(&mut output),
             ));
@@ -439,7 +439,7 @@ impl<E: stats::SysEvents + 'static> worker::SimpleWorker for MassRebuildWorker<E
                         state = hubcaps::statuses::State::Failure;
                         gist_url = make_gist(
                             &gists,
-                            check.name(),
+                            &check.name(),
                             Some(format!("{:?}", state)),
                             file_to_str(&mut out),
                         );
@@ -511,7 +511,7 @@ impl<E: stats::SysEvents + 'static> worker::SimpleWorker for MassRebuildWorker<E
                     state = hubcaps::statuses::State::Failure;
                     gist_url = make_gist(
                         &gists,
-                        String::from("Meta Check"),
+                        "Meta Check",
                         Some(format!("{:?}", state)),
                         file_to_str(&mut out),
                     );
@@ -534,17 +534,17 @@ impl<E: stats::SysEvents + 'static> worker::SimpleWorker for MassRebuildWorker<E
             }
             update_labels(
                 &issue,
-                stdenvtagger.tags_to_add(),
-                stdenvtagger.tags_to_remove(),
+                &stdenvtagger.tags_to_add(),
+                &stdenvtagger.tags_to_remove(),
             );
 
             if let Some((removed, added)) = rebuildsniff.package_diff() {
             let mut addremovetagger = PkgsAddedRemovedTagger::new();
-                addremovetagger.changed(removed, added);
+                addremovetagger.changed(&removed, &added);
                 update_labels(
                     &issue,
-                    addremovetagger.tags_to_add(),
-                    addremovetagger.tags_to_remove(),
+                    &addremovetagger.tags_to_add(),
+                    &addremovetagger.tags_to_remove(),
                 );
             }
 
@@ -553,7 +553,7 @@ impl<E: stats::SysEvents + 'static> worker::SimpleWorker for MassRebuildWorker<E
                 if attrs.len() > 0 {
                     let gist_url = make_gist(
                         &gists,
-                        String::from("Changed Paths"),
+                        "Changed Paths",
                         Some("".to_owned()),
                         attrs
                             .iter()
@@ -570,8 +570,8 @@ impl<E: stats::SysEvents + 'static> worker::SimpleWorker for MassRebuildWorker<E
 
             update_labels(
                 &issue,
-                rebuild_tags.tags_to_add(),
-                rebuild_tags.tags_to_remove(),
+                &rebuild_tags.tags_to_add(),
+                &rebuild_tags.tags_to_remove(),
             );
 
             overall_status.set_with_description("^.^!", hubcaps::statuses::State::Success);
@@ -593,15 +593,15 @@ impl<E: stats::SysEvents + 'static> worker::SimpleWorker for MassRebuildWorker<E
 
 fn make_gist<'a>(
     gists: &hubcaps::gists::Gists<'a>,
-    name: String,
+    name: &str,
     description: Option<String>,
     contents: String,
 ) -> Option<String> {
-    let mut files = HashMap::new();
+    let mut files: HashMap<String, hubcaps::gists::Content> = HashMap::new();
     files.insert(
-        name.clone(),
+        name.to_string(),
         hubcaps::gists::Content {
-            filename: Some(name.clone()),
+            filename: Some(name.to_string()),
             content: contents,
         },
     );
@@ -618,7 +618,7 @@ fn make_gist<'a>(
     )
 }
 
-pub fn update_labels(issue: &hubcaps::issues::IssueRef, add: Vec<String>, remove: Vec<String>) {
+pub fn update_labels(issue: &hubcaps::issues::IssueRef, add: &Vec<String>, remove: &Vec<String>) {
     let l = issue.labels();
 
     let existing: Vec<String> = issue
@@ -649,7 +649,7 @@ pub fn update_labels(issue: &hubcaps::issues::IssueRef, add: Vec<String>, remove
     }
 }
 
-fn parse_commit_messages(messages: Vec<String>) -> Vec<String> {
+fn parse_commit_messages(messages: &[String]) -> Vec<String> {
     messages
         .iter()
         .filter_map(|line| {
@@ -689,7 +689,7 @@ mod tests {
         ];
         assert_eq!(
             parse_commit_messages(
-                "
+                &"
               firefox{-esr,}: fix failing build due to the google-api-key
               Merge pull request #34483 from andir/dovecot-cve-2017-15132
               firefox: enable official branding
@@ -705,7 +705,7 @@ mod tests {
             "
                     .lines()
                     .map(|l| l.to_owned())
-                    .collect(),
+                    .collect::<Vec<String>>(),
             ),
             expect
         );