Remove usages of ChangesetId::is_empty

Summary: This is being removed in favor of `Option<ChangesetId>` which achieves the same effect. This diff makes changes at the level of `gitimport`, `remote-gitimport` and `Mononoke Git Server`. Follow up diff in the stack would update the `GitUploader` interface to expect `Option<ChangesetId>` instead of `ChangesetId`.

Reviewed By: gustavoavena

Differential Revision: D68438640

fbshipit-source-id: 6416bcac7a14e47745ca158d0b4a5a140343bea9

eden/mononoke/git/gitimport/src/main.rs

@@ -473,7 +473,7 @@ async fn async_main(app: MononokeApp) -> Result<(), Error> {
                         &ref_name,
                         tag_id,
                         &existing_tags,
-                        &ChangesetId::empty(),
+                        None, // No changeset for content refs
                         reupload,
                         uploader.clone(),
                         reader.clone(),
@@ -526,7 +526,7 @@ async fn async_main(app: MononokeApp) -> Result<(), Error> {
                         &name,
                         tag_id,
                         &existing_tags,
-                        changeset,
+                        Some(*changeset),
                         reupload,
                         uploader.clone(),
                         reader.clone(),
@@ -603,7 +603,7 @@ async fn process_tags<Uploader: GitUploader, Reader: GitReader>(
     name: &String,
     tag_id: ObjectId,
     existing_tags: &HashMap<String, GitSha1>,
-    changeset: &ChangesetId,
+    changeset: Option<ChangesetId>,
     reupload: ReuploadCommits,
     uploader: Arc<Uploader>,
     reader: Arc<Reader>,

eden/mononoke/git/import_tools/src/lib.rs

@@ -219,15 +219,16 @@ pub async fn create_changeset_for_annotated_tag<Uploader: GitUploader, Reader: G
     reader: Arc<Reader>,
     tag_id: &ObjectId,
     maybe_tag_name: Option<String>,
-    original_changeset_id: &ChangesetId,
+    original_changeset_id: Option<ChangesetId>,
 ) -> Result<ChangesetId> {
     // Get the parsed Git Tag
     let tag_metadata = TagMetadata::new(ctx, *tag_id, maybe_tag_name, &reader)
         .await
         .with_context(|| format_err!("Failed to create TagMetadata from git tag {}", tag_id))?;
     // Create the corresponding changeset for the Git Tag at Mononoke end
+    let original_changeset_id = original_changeset_id.unwrap_or_else(ChangesetId::empty);
     let changeset_id = uploader
-        .generate_changeset_for_annotated_tag(ctx, *original_changeset_id, tag_metadata)
+        .generate_changeset_for_annotated_tag(ctx, original_changeset_id, tag_metadata)
         .await
         .with_context(|| format_err!("Failed to generate changeset for git tag {}", tag_id))?;
     Ok(changeset_id)

eden/mononoke/git_server/src/service/uploader.rs

@@ -50,12 +50,12 @@ type ContentTags = HashMap<String, ObjectId>;
 #[derive(Clone, Debug)]
 struct TagMetadata {
     name: Option<String>,
-    bonsai_target: ChangesetId,
+    bonsai_target: Option<ChangesetId>,
     git_target: ObjectId,
 }
 
 impl TagMetadata {
-    fn new(name: Option<String>, bonsai_target: ChangesetId, git_target: ObjectId) -> Self {
+    fn new(name: Option<String>, bonsai_target: Option<ChangesetId>, git_target: ObjectId) -> Self {
         Self {
             name,
             bonsai_target,
@@ -178,12 +178,12 @@ async fn tags(
         if let Some(tag) = object.parsed.as_tag() {
             let (target_id, kind) = peel_tag_target(tag, object_store).await?;
             let bonsai_id = if let Some(bonsai_id) = ref_map.commit_bonsai_by_oid(&target_id) {
-                bonsai_id
+                Some(bonsai_id)
             } else if kind != Kind::Commit {
                 // If the target is not a commit, we can't create a changeset for it
-                ChangesetId::empty()
+                None
             } else {
-                git_to_bonsai(ctx, repo, &target_id).await?
+                Some(git_to_bonsai(ctx, repo, &target_id).await?)
             };
             result.insert(id.clone(), TagMetadata::new(None, bonsai_id, target_id));
         }
@@ -225,8 +225,8 @@ async fn process_tags<Uploader: GitUploader>(
         } = tag_metadata;
         // Add a mapping from the tag object id to the commit changeset id where it points. This will later
         // be used in bookmark movement
-        if !bonsai_target.is_empty() {
-            ref_map.insert_tag(&tag_id, bonsai_target);
+        if let Some(bonsai_target) = bonsai_target.as_ref() {
+            ref_map.insert_tag(&tag_id, *bonsai_target);
         } else if let Some(name) = name.as_ref() {
             content_tags.insert(format!("refs/{}", name), git_target);
         }
@@ -239,7 +239,7 @@ async fn process_tags<Uploader: GitUploader>(
             object_store.clone(),
             &tag_id,
             name,
-            &bonsai_target,
+            bonsai_target,
         )
         .await?;
     }

eden/mononoke/mononoke_types/src/typed_hash.rs

@@ -98,10 +98,6 @@ impl ChangesetId {
     pub fn empty() -> Self {
         Self(Blake2::from_byte_array([0; 32]))
     }
-
-    pub fn is_empty(&self) -> bool {
-        self.0.into_inner() == [0; 32]
-    }
 }
 
 /// An identifier for a changeset hash prefix in Mononoke.