Fix allow_auto_merge in combination with repository archiving

src/github/api/mod.rs

@@ -258,7 +258,8 @@ pub(crate) struct Repo {
     pub(crate) description: Option<String>,
     pub(crate) homepage: Option<String>,
     pub(crate) archived: bool,
-    pub(crate) allow_auto_merge: bool,
+    #[serde(default)]
+    pub(crate) allow_auto_merge: Option<bool>,
 }
 
 fn repo_owner<'de, D>(deserializer: D) -> Result<String, D::Error>

src/github/api/write.rs

@@ -236,7 +236,7 @@ impl GitHubWrite {
                 description: settings.description.clone(),
                 homepage: settings.homepage.clone(),
                 archived: false,
-                allow_auto_merge: settings.auto_merge_enabled,
+                allow_auto_merge: Some(settings.auto_merge_enabled),
             })
         } else {
             Ok(self

src/github/mod.rs

@@ -261,7 +261,7 @@ impl SyncGitHub {
             description: actual_repo.description.clone(),
             homepage: actual_repo.homepage.clone(),
             archived: actual_repo.archived,
-            auto_merge_enabled: actual_repo.allow_auto_merge,
+            auto_merge_enabled: actual_repo.allow_auto_merge.unwrap_or(false),
         };
         let new_settings = RepoSettings {
             description: Some(expected_repo.description.clone()),
@@ -629,12 +629,30 @@ struct UpdateRepoDiff {
 
 impl UpdateRepoDiff {
     pub(crate) fn noop(&self) -> bool {
+        if !self.can_be_modified() {
+            return true;
+        }
+
         self.settings_diff.0 == self.settings_diff.1
             && self.permission_diffs.is_empty()
             && self.branch_protection_diffs.is_empty()
     }
 
+    fn can_be_modified(&self) -> bool {
+        // Archived repositories cannot be modified
+        // If the repository should be archived, and we do not change its archival status,
+        // we should not change any other properties of the repo.
+        if self.settings_diff.1.archived && self.settings_diff.0.archived {
+            return false;
+        }
+        true
+    }
+
     fn apply(&self, sync: &GitHubWrite) -> anyhow::Result<()> {
+        if !self.can_be_modified() {
+            return Ok(());
+        }
+
         if self.settings_diff.0 != self.settings_diff.1 {
             sync.edit_repo(&self.org, &self.name, &self.settings_diff.1)?;
         }