fix: support annotated tags in cog check -l

Annotated tags are unique git objects with their own hashes.
Consequently, prior to this commit, cog check would not recognize these
tags in the commit ranges it checked.

This commit fixes this bug by detecting if a tag is an annotated tag,
and identifying its associated commit.

Fixes #151.

cog.toml

@@ -53,4 +53,5 @@ authors = [
     { signature = "orhun", username = "orhun" },
     { signature = "Danny Tatom", username = "its-danny" },
     { signature = "Clément Poissonnier", username = "cpoissonnier" },
-]
+    { signature = "Luke Hsiao", username = "lukehsiao" },
+]

src/git/revspec.rs

@@ -243,9 +243,22 @@ impl Repository {
 
         let mut tags = vec![];
         self.0
-            .tag_foreach(|oid, name| {
+            .tag_foreach(|mut oid, name| {
                 let name = String::from_utf8_lossy(name);
                 let name = name.as_ref().strip_prefix("refs/tags/").unwrap();
+
+                // If this is an annotated tag, find the first parent commit
+                if self.0.revparse_single(name).unwrap().as_commit().is_none() {
+                    if let Some(commit) = self
+                        .0
+                        .revparse_single([name, "^{}"].concat().as_str())
+                        .unwrap()
+                        .as_commit()
+                    {
+                        oid = commit.id();
+                    }
+                };
+
                 if range.contains(&oid) {
                     if let Ok(tag) = Tag::new(name, Some(oid)) {
                         tags.push(tag);
@@ -361,6 +374,48 @@ mod test {
         Ok(())
     }
 
+    #[sealed_test]
+    fn get_annotated_tag_commits() -> Result<()> {
+        // Arrange
+        let repo = Repository::init(".")?;
+        run_cmd!(
+            git init
+            echo changes > file
+            git add .
+        )?;
+
+        let start = repo.commit("chore: init")?;
+
+        run_cmd!(
+            git init
+            echo changes > file2
+            git add .
+        )?;
+
+        let _end = repo.commit("chore: 1.0.0")?;
+
+        // Create an annotated tag
+        let head = repo.get_head_commit().unwrap();
+        let sig = git2::Signature::now("Author", "email@example.com")?;
+        repo.0
+            .tag("1.0.0", &head.into_object(), &sig, "the_msg", false)?;
+
+        run_cmd!(
+            git init
+            echo changes > file3
+            git add .
+        )?;
+
+        repo.commit("feat: a commit")?;
+
+        let commit_range = repo.get_commit_range(&RevspecPattern::from("..1.0.0"))?;
+
+        assert_that!(commit_range.from).is_equal_to(OidOf::Other(start));
+        assert_that!(commit_range.to.to_string()).is_equal_to("1.0.0".to_string());
+        assert_that!(commit_range.commits).has_length(1);
+        Ok(())
+    }
+
     #[sealed_test]
     fn get_tag_commits() -> Result<()> {
         // Arrange