fix fetch MimeType fail for git

src/main/java/com/imyeyu/server/modules/git/service/implement/RepositoryServiceImplement.java

@@ -175,7 +175,7 @@ public class RepositoryServiceImplement implements RepositoryService {
 				// 根据文件名猜测
 				return new MimetypesFileTypeMap().getContentType(Network.uriFileName(path));
 			} else {
-				repoPath = "%s/%s.git".formatted(repoPath, repoName);
+				repoPath = "%s/%s.git".formatted(repoPath, repoName.toLowerCase());
 				// 仓库
 				@Cleanup
 				org.eclipse.jgit.lib.Repository repo = new FileRepositoryBuilder().setGitDir(Path.of(repoPath).toFile()).build();