fix: fixed merge commits detection (#136)

When searching for commits, `go-git` uses depth-first search by default.
In cases where commits are brought in via a merge commit, the commits
other than the merge commit itself will be missed, as the DFS will go
down the commits directly from HEAD, and will exit upon finding the previous
tag, before then searching other paths. This is fixed by using the sort
orders `LogOrderCommitterTime` or `LogOrderBSF`. Here `LogOrderCommitterTime`
was used as the `go-git` documentation says it has the highest compatibility
with the `git log` CLI command.

git/commits.go

@@ -29,7 +29,10 @@ func GetConventionalCommitTypesSinceLastRelease(repository *git.Repository) (Con
 		}
 		return ConventionalCommmitTypesResult{}, err
 	}
-	commitIterator, err := repository.Log(&git.LogOptions{From: head.Hash()})
+	commitIterator, err := repository.Log(&git.LogOptions{
+		From:  head.Hash(),
+		Order: git.LogOrderCommitterTime,
+	})
 	if err != nil {
 		return ConventionalCommmitTypesResult{}, err
 	}