diff --git a/.gitignore b/.gitignore
@@ -1,2 +1,4 @@
 build/
 __pycache__/
+.cache/
+compile_commands.json
diff --git a/CMakeLists.txt b/CMakeLists.txt
@@ -39,6 +39,8 @@ find_package(libgit2)
 # =====
 
 set(GIT2CPP_SRC
+    ${GIT2CPP_SOURCE_DIR}/subcommand/add_subcommand.cpp
+    ${GIT2CPP_SOURCE_DIR}/subcommand/add_subcommand.hpp
     ${GIT2CPP_SOURCE_DIR}/subcommand/init_subcommand.cpp
     ${GIT2CPP_SOURCE_DIR}/subcommand/init_subcommand.hpp
     ${GIT2CPP_SOURCE_DIR}/subcommand/status_subcommand.cpp
@@ -47,6 +49,8 @@ set(GIT2CPP_SRC
     ${GIT2CPP_SOURCE_DIR}/utils/common.hpp
     ${GIT2CPP_SOURCE_DIR}/utils/git_exception.cpp
     ${GIT2CPP_SOURCE_DIR}/utils/git_exception.hpp
+    ${GIT2CPP_SOURCE_DIR}/wrapper/index_wrapper.cpp
+    ${GIT2CPP_SOURCE_DIR}/wrapper/index_wrapper.hpp
     ${GIT2CPP_SOURCE_DIR}/wrapper/refs_wrapper.cpp
     ${GIT2CPP_SOURCE_DIR}/wrapper/refs_wrapper.hpp
     ${GIT2CPP_SOURCE_DIR}/wrapper/repository_wrapper.cpp
@@ -59,4 +63,3 @@ set(GIT2CPP_SRC
 
 add_executable(git2cpp ${GIT2CPP_SRC})
 target_link_libraries(git2cpp PRIVATE libgit2::libgit2package)
-
diff --git a/README.md b/README.md
@@ -13,7 +13,7 @@ Developer's workflow using `micromamba` to manage the dependencies:
 ```bash
 micromamba create -f dev-environment.yml
 micromamba activate git2cpp-dev
-cmake -Bbuild $CMAKE_INSALL_PREFIX=$CONDA_PREFIX
+cmake -Bbuild -DCMAKE_INSTALL_PREFIX=$CONDA_PREFIX
 cd build
 make -j8
 ```

diff --git a/dev-environment.yml b/dev-environment.yml
@@ -4,7 +4,7 @@ channels:
 dependencies:
   - cli11
   - libgit2
-  - meson
+  - cmake
   - pkg-config
   - python
   - pytest

diff --git a/src/main.cpp b/src/main.cpp
@@ -4,6 +4,7 @@
 
 #include "utils/git_exception.hpp"
 #include "version.hpp"
+#include "subcommand/add_subcommand.hpp"
 #include "subcommand/init_subcommand.hpp"
 #include "subcommand/status_subcommand.hpp"
 
@@ -21,6 +22,7 @@ int main(int argc, char** argv)
         // Sub commands
         init_subcommand init(lg2_obj, app);
         status_subcommand status(lg2_obj, app);
+        add_subcommand add(lg2_obj, app);
 
         app.parse(argc, argv);
 

diff --git a/src/subcommand/add_subcommand.cpp b/src/subcommand/add_subcommand.cpp
@@ -0,0 +1,39 @@
+#include <git2.h>
+
+#include "add_subcommand.hpp"
+#include "../wrapper/index_wrapper.hpp"
+#include "../wrapper/repository_wrapper.hpp"
+
+
+add_subcommand::add_subcommand(const libgit2_object&, CLI::App& app)
+{
+    auto *sub = app.add_subcommand("add", "Add file contents to the index");
+
+    sub->add_option("files", m_add_files, "Files to add");
+
+    sub->add_flag("-A,--all,--no-ignore-removal", m_all_flag, "");
+    // sub->add_flag("-n,--dryrun", dryrun_flag, "");
+    // sub->add_flag("-u,--update", update_flag, "");
+    // sub->add_flag("-v,--verbose", verbose_flag, "");
+
+    sub->callback([this]() { this->run(); });
+};
+
+
+void add_subcommand::run()
+{
+    auto directory = get_current_git_path();
+    auto bare = false;
+    auto repo = repository_wrapper::init(directory, bare);
+
+    index_wrapper index = repo.make_index();
+
+    if (m_all_flag)
+    {
+        index.add_all();
+    }
+    else
+    {
+        index.add_entries(m_add_files);
+    }
+}
diff --git a/src/subcommand/add_subcommand.hpp b/src/subcommand/add_subcommand.hpp
@@ -0,0 +1,17 @@
+#pragma once
+
+#include <CLI/CLI.hpp>
+
+#include "../utils/common.hpp"
+
+class add_subcommand
+{
+public:
+
+    explicit add_subcommand(const libgit2_object&, CLI::App& app);
+    void run();
+
+private:
+    bool m_all_flag = false;
+    std::vector<std::string> m_add_files;
+};
diff --git a/src/subcommand/init_subcommand.cpp b/src/subcommand/init_subcommand.cpp
@@ -6,10 +6,10 @@ init_subcommand::init_subcommand(const libgit2_object&, CLI::App& app)
 {
     auto *sub = app.add_subcommand("init", "Explanation of init here");
 
-    sub->add_flag("--bare", bare, "info about bare arg");
+    sub->add_flag("--bare", m_bare, "info about bare arg");
 
     // If directory not specified, uses cwd.
-    sub->add_option("directory", directory, "info about directory arg")
+    sub->add_option("directory", m_directory, "info about directory arg")
         ->check(CLI::ExistingDirectory | CLI::NonexistentPath)
         ->default_val(get_current_git_path());
 
@@ -18,5 +18,5 @@ init_subcommand::init_subcommand(const libgit2_object&, CLI::App& app)
 
 void init_subcommand::run()
 {
-    repository_wrapper::init(directory, bare);
+    repository_wrapper::init(m_directory, m_bare);
 }
diff --git a/src/subcommand/init_subcommand.hpp b/src/subcommand/init_subcommand.hpp
@@ -14,6 +14,6 @@ class init_subcommand
     void run();
 
 private:
-    bool bare;
-    std::string directory;
+    bool m_bare;
+    std::string m_directory;
 };
diff --git a/src/subcommand/status_subcommand.cpp b/src/subcommand/status_subcommand.cpp
@@ -13,19 +13,14 @@
 status_subcommand::status_subcommand(const libgit2_object&, CLI::App& app)
 {
     auto *sub = app.add_subcommand("status", "Show modified files in working directory, staged for your next commit");
-    // Displays paths that have differences between the index file and the current HEAD commit,
-    // paths that have differences between the working tree and the index file, and paths in the
-    // working tree that are not tracked by Git (and are not ignored by gitignore[5]).
-    // The first are what you would commit by running git commit;
-    // the second and third are what you could commit by running git add before running git commit.
 
-    sub->add_flag("-s,--short", short_flag, "Give the output in the short-format.");
-    sub->add_flag("--long", long_flag, "Give the output in the long-format. This is the default.");
+    sub->add_flag("-s,--short", m_short_flag, "Give the output in the short-format.");
+    sub->add_flag("--long", m_long_flag, "Give the output in the long-format. This is the default.");
     // sub->add_flag("--porcelain[=<version>]", porcelain, "Give the output in an easy-to-parse format for scripts.
     //     This is similar to the short output, but will remain stable across Git versions and regardless of user configuration.
     //     See below for details. The version parameter is used to specify the format version. This is optional and defaults
     //     to the original version v1 format.");
-    sub->add_flag("-b,--branch", branch_flag, "Show the branch and tracking info even in short-format.");
+    sub->add_flag("-b,--branch", m_branch_flag, "Show the branch and tracking info even in short-format.");
 
     sub->callback([this]() { this->run(); });
 };
@@ -152,7 +147,7 @@ void print_entries(std::vector<print_entry> entries_to_print)
     }
 }
 
-void print_not_tracked(std::vector<print_entry> entries_to_print, const std::set<std::string>& tracked_dir_set,
+void print_not_tracked(const std::vector<print_entry>& entries_to_print, const std::set<std::string>& tracked_dir_set,
         std::set<std::string>& untracked_dir_set)
 {
     std::vector<print_entry> not_tracked_entries_to_print{};
@@ -199,11 +194,11 @@ void status_subcommand::run()
     std::vector<std::string> ignored_to_print{};
 
     output_format of = output_format::DEFAULT;
-    if (short_flag)
+    if (m_short_flag)
     {
         of = output_format::SHORT;
     }
-    if (long_flag)
+    if (m_long_flag)
     {
         of = output_format::LONG;
     }
@@ -220,7 +215,7 @@ void status_subcommand::run()
     }
     else
     {
-        if (branch_flag)
+        if (m_branch_flag)
         {
             std::cout  << "## " << branch_name << std::endl;
         }

diff --git a/src/subcommand/status_subcommand.hpp b/src/subcommand/status_subcommand.hpp
@@ -12,7 +12,7 @@ class status_subcommand
     void run();
 
 private:
-    bool branch_flag = false;
-    bool long_flag = false;
-    bool short_flag = false;
+    bool m_branch_flag = false;
+    bool m_long_flag = false;
+    bool m_short_flag = false;
 };
diff --git a/src/utils/common.hpp b/src/utils/common.hpp
@@ -36,7 +36,7 @@ class wrapper_base
     wrapper_base& operator=(wrapper_base&& rhs)
     {
         std::swap(p_resource, rhs.p_resource);
-        return this;
+        return *this;
     }
 
     operator resource_type*() const noexcept

diff --git a/src/utils/meson.build b/src/utils/meson.build
diff --git a/src/version.hpp b/src/version.hpp
@@ -2,7 +2,7 @@
 
 #define GIT2CPP_VERSION_MAJOR 0
 #define GIT2CPP_VERSION_MINOR 0
-#define GIT2CPP_VERSION_PATCH 1
+#define GIT2CPP_VERSION_PATCH 2
 
 // e.g. ".rc0"
 #define GIT2CPP_VERSION_SUFFIX

diff --git a/src/wrapper/index_wrapper.cpp b/src/wrapper/index_wrapper.cpp
@@ -0,0 +1,35 @@
+#include "index_wrapper.hpp"
+#include "../utils/git_exception.hpp"
+#include "../wrapper/repository_wrapper.hpp"
+
+#include <vector>
+
+index_wrapper::~index_wrapper()
+{
+    git_index_free(p_resource);
+    p_resource=nullptr;
+}
+
+index_wrapper index_wrapper::init(repository_wrapper& rw)
+{
+    index_wrapper index;
+    throwIfError(git_repository_index(&(index.p_resource), rw));
+    return index;
+}
+
+void index_wrapper::add_entries(std::vector<std::string> patterns)
+{
+    add_impl(std::move(patterns));
+}
+
+void index_wrapper::add_all()
+{
+    add_impl({{"."}});
+}
+
+void index_wrapper::add_impl(std::vector<std::string> patterns)
+{
+    git_strarray_wrapper array{patterns};
+    throwIfError(git_index_add_all(*this, array, 0, NULL, NULL));
+    throwIfError(git_index_write(*this));
+}
diff --git a/src/wrapper/index_wrapper.hpp b/src/wrapper/index_wrapper.hpp
@@ -0,0 +1,31 @@
+#pragma once
+
+#include <string>
+#include <vector>
+
+#include <git2.h>
+
+#include "../utils/common.hpp"
+
+class repository_wrapper;
+
+class index_wrapper : public wrapper_base<git_index>
+{
+public:
+
+    ~index_wrapper();
+
+    index_wrapper(index_wrapper&&) = default;
+    index_wrapper& operator=(index_wrapper&&) = default;
+
+    static index_wrapper init(repository_wrapper& rw);
+
+    void add_entries(std::vector<std::string> patterns);
+    void add_all();
+
+
+private:
+
+    index_wrapper() = default;
+    void add_impl(std::vector<std::string> patterns);
+};
diff --git a/src/wrapper/repository_wrapper.cpp b/src/wrapper/repository_wrapper.cpp
@@ -1,6 +1,5 @@
-#include "../utils/git_exception.hpp"
 #include "repository_wrapper.hpp"
-
+#include "../utils/git_exception.hpp"
 
 repository_wrapper::~repository_wrapper()
 {
@@ -21,3 +20,9 @@ repository_wrapper repository_wrapper::init(const std::string& directory, bool b
     throwIfError(git_repository_init(&(rw.p_resource), directory.c_str(), bare));
     return rw;
 }
+
+index_wrapper repository_wrapper::make_index()
+{
+    index_wrapper index = index_wrapper::init(*this);
+    return index;
+}
diff --git a/src/wrapper/repository_wrapper.hpp b/src/wrapper/repository_wrapper.hpp
@@ -5,6 +5,7 @@
 #include <git2.h>
 
 #include "../utils/common.hpp"
+#include "../wrapper/index_wrapper.hpp"
 
 class repository_wrapper : public wrapper_base<git_repository>
 {
@@ -17,6 +18,7 @@ class repository_wrapper : public wrapper_base<git_repository>
 
     static repository_wrapper init(const std::string& directory, bool bare);
     static repository_wrapper open(const std::string& directory);
+    index_wrapper make_index();
 
 private:
 

diff --git a/test/data/status_data/embeded_git/config b/test/data/status_data/embeded_git/config
diff --git a/test/test_add.py b/test/test_add.py
@@ -0,0 +1,36 @@
+import os
+import subprocess
+
+import pytest
+
+
+@pytest.mark.parametrize("all_flag", ["", "-A", "--all", "--no-ignore-removal"])
+def test_add(git2cpp_path, all_flag):
+    with open("./test/mook_file.txt", "x") as f:
+        pass
+
+    with open("./test/mook_file_2.txt", "x") as f:
+        pass
+
+    cmd_add = [git2cpp_path, 'add']
+    if all_flag != "":
+        cmd_add.append(all_flag)
+    else:
+        cmd_add.append("test/mook_file.txt")
+    subprocess.run(cmd_add, capture_output=True, text=True)
+
+    cmd_status = [git2cpp_path, 'status', "--long"]
+    p_status = subprocess.run(cmd_status, capture_output=True, text=True)
+
+    assert "Changes to be committed" in p_status.stdout
+    assert "new file" in p_status.stdout
+    if all_flag != "":
+        assert "Untracked files" not in p_status.stdout
+    else:
+        assert "Untracked files" in p_status.stdout
+
+    os.remove("./test/mook_file.txt")
+    os.remove("./test/mook_file_2.txt")
+
+    # undo the add, to leave the test directory at the end the same as it was at the start
+    subprocess.run(cmd_add, capture_output=True, text=True)
-Original file line number
+Diff line change
@@ Expand Up / @@ -4,7 +4,7 @@ channels: @@
     dependencies:
       - cli11
       - libgit2
-      - meson
+      - cmake
       - pkg-config
       - python
       - pytest
@@ Expand Down @@