core: Implement basic git integration

Missing streaming, so git's a bit confused, but works.

Also easy to bypass. Although I doubt any mf at alibaba gon bypass it
with his custom UA.

src/headers/gitProtocolHeader.hpp

@@ -0,0 +1,24 @@
+#include <pistache/http_headers.h>
+#include <pistache/net.h>
+
+class GitProtocolHeader : public Pistache::Http::Header::Header {
+  public:
+    NAME("Git-Protocol");
+
+    GitProtocolHeader() = default;
+
+    void parse(const std::string& str) override {
+        m_text = str;
+    }
+
+    void write(std::ostream& os) const override {
+        os << m_text;
+    }
+
+    std::string text() const {
+        return m_text;
+    }
+
+  private:
+    std::string m_text = "";
+};