[M8] cargoxx-git dependencies: { git = ..., rev = ... } deps

src/manifest/manifest.cppm

@@ -8,6 +8,7 @@ export namespace cargoxx::manifest {
 enum class DepSource {
     Auto,         // string form or { version = ... } only → existing resolver chain
     CargoxxPath,  // { path = "../foo" } → recursive cargoxx build
+    CargoxxGit,   // { git = "...", rev = "..." } → fetch + recursive cargoxx build
 };
 
 struct Dependency {
@@ -15,7 +16,9 @@ struct Dependency {
     std::string version_spec;
     std::vector<std::string> components;
     DepSource source = DepSource::Auto;
-    std::optional<std::string> path;  // when source == CargoxxPath
+    std::optional<std::string> path;     // when source == CargoxxPath
+    std::optional<std::string> git_url;  // when source == CargoxxGit
+    std::optional<std::string> git_rev;  // when source == CargoxxGit (40-char)
 
     bool operator==(const Dependency&) const = default;
 };