[vcpkg registries] Add git registries (#15054)

* [vcpkg registries] Add git registries support

* Add git registries support to the registries module of vcpkg.
* add e2e tests for git registries
* fix vcpkg.cmake for registries

* fix CRs, remove a thing

* better error messages

* Billy CRs

* fix Robert's CR comment

* I learned about `-c` today

* format

* fix baseline.json

* failing to find baseline is technically not a bug

3 files changed, 69 insertions, 0 deletions

diff --git a/toolsrc/include/vcpkg/base/files.h b/toolsrc/include/vcpkg/base/files.h
index e1628eaf0..dd1b3a6c6 100644
--- a/toolsrc/include/vcpkg/base/files.h
+++ b/toolsrc/include/vcpkg/base/files.h
@@ -125,6 +125,12 @@ namespace fs
 
 #endif
 
+    inline bool operator==(SystemHandle lhs, SystemHandle rhs) noexcept
+    {
+        return lhs.system_handle == rhs.system_handle;
+    }
+    inline bool operator!=(SystemHandle lhs, SystemHandle rhs) noexcept { return !(lhs == rhs); }
+
     inline bool is_symlink(file_status s) noexcept
     {
 #if defined(_WIN32)
@@ -266,4 +272,55 @@ namespace vcpkg::Files
 #if defined(_WIN32)
     fs::path win32_fix_path_case(const fs::path& source);
 #endif // _WIN32
+
+    struct ExclusiveFileLock
+    {
+        enum class Wait
+        {
+            Yes,
+            No,
+        };
+
+        ExclusiveFileLock() = default;
+        ExclusiveFileLock(ExclusiveFileLock&& other)
+            : fs_(other.fs_), handle_(std::exchange(handle_, fs::SystemHandle{}))
+        {
+        }
+        ExclusiveFileLock& operator=(ExclusiveFileLock&& other)
+        {
+            if (this == &other) return *this;
+
+            clear();
+            fs_ = other.fs_;
+            handle_ = std::exchange(other.handle_, fs::SystemHandle{});
+            return *this;
+        }
+
+        ExclusiveFileLock(Wait wait, Filesystem& fs, const fs::path& path_, std::error_code& ec) : fs_(&fs)
+        {
+            switch (wait)
+            {
+                case Wait::Yes: handle_ = fs_->take_exclusive_file_lock(path_, ec); break;
+                case Wait::No: handle_ = fs_->try_take_exclusive_file_lock(path_, ec); break;
+            }
+        }
+        ~ExclusiveFileLock() { clear(); }
+
+        explicit operator bool() const { return handle_.is_valid(); }
+        bool has_lock() const { return handle_.is_valid(); }
+
+        void clear()
+        {
+            if (fs_ && handle_.is_valid())
+            {
+                std::error_code ignore;
+                fs_->unlock_file_lock(std::exchange(handle_, fs::SystemHandle{}), ignore);
+            }
+        }
+
+    private:
+        fs::SystemHandle handle_;
+        Filesystem* fs_;
+    };
+
 }
diff --git a/toolsrc/include/vcpkg/base/system.h b/toolsrc/include/vcpkg/base/system.h
index 8e45f6538..da14fa4bb 100644
--- a/toolsrc/include/vcpkg/base/system.h
+++ b/toolsrc/include/vcpkg/base/system.h
@@ -20,6 +20,8 @@ namespace vcpkg::System
 
     Optional<std::string> get_registry_string(void* base_hkey, StringView subkey, StringView valuename);
 
+    long get_process_id();
+
     enum class CPUArchitecture
     {
         X86,
diff --git a/toolsrc/include/vcpkg/vcpkgpaths.h b/toolsrc/include/vcpkg/vcpkgpaths.h
index a175d51e2..36447b9f3 100644
--- a/toolsrc/include/vcpkg/vcpkgpaths.h
+++ b/toolsrc/include/vcpkg/vcpkgpaths.h
@@ -124,6 +124,16 @@ namespace vcpkg
 
         ExpectedS<std::map<std::string, std::string, std::less<>>> git_get_local_port_treeish_map() const;
 
+        // Git manipulation for remote registries
+        // runs `git fetch {uri} {treeish}`, and returns the hash of FETCH_HEAD.
+        // If `treeish` is empty, then just runs `git fetch {uri}`
+        ExpectedS<std::string> git_fetch_from_remote_registry(StringView uri, StringView treeish = {}) const;
+        ExpectedS<std::string> git_show_from_remote_registry(StringView hash,
+                                                             const fs::path& relative_path_to_file) const;
+        ExpectedS<std::string> git_find_object_id_for_remote_registry_path(StringView hash,
+                                                                           const fs::path& relative_path_to_file) const;
+        ExpectedS<fs::path> git_checkout_object_from_remote_registry(StringView tree) const;
+
         Optional<const Json::Object&> get_manifest() const;
         Optional<const fs::path&> get_manifest_path() const;
         const Configuration& get_configuration() const;