Add merge subcommand (fastforward) (#48)

* Add merge subcommand (fastforward)

* comment unused code

* clean code

* address review comments

Author: SandrineP

CMakeLists.txt

@@ -54,6 +54,8 @@ set(GIT2CPP_SRC
     ${GIT2CPP_SOURCE_DIR}/subcommand/init_subcommand.hpp
     ${GIT2CPP_SOURCE_DIR}/subcommand/log_subcommand.cpp
     ${GIT2CPP_SOURCE_DIR}/subcommand/log_subcommand.hpp
+    ${GIT2CPP_SOURCE_DIR}/subcommand/merge_subcommand.cpp
+    ${GIT2CPP_SOURCE_DIR}/subcommand/merge_subcommand.hpp
     ${GIT2CPP_SOURCE_DIR}/subcommand/reset_subcommand.cpp
     ${GIT2CPP_SOURCE_DIR}/subcommand/reset_subcommand.hpp
     ${GIT2CPP_SOURCE_DIR}/subcommand/status_subcommand.cpp

src/main.cpp

@@ -1,4 +1,5 @@
 #include <CLI/CLI.hpp>
+#include <cmath>
 #include <git2.h>  // For version number only
 #include <iostream>
 
@@ -11,6 +12,7 @@
 #include "subcommand/commit_subcommand.hpp"
 #include "subcommand/init_subcommand.hpp"
 #include "subcommand/log_subcommand.hpp"
+#include "subcommand/merge_subcommand.hpp"
 #include "subcommand/reset_subcommand.hpp"
 #include "subcommand/status_subcommand.hpp"
 
@@ -35,6 +37,7 @@ int main(int argc, char** argv)
         commit_subcommand commit(lg2_obj, app);
         reset_subcommand reset(lg2_obj, app);
         log_subcommand log(lg2_obj, app);
+        merge_subcommand merge(lg2_obj, app);
 
         app.require_subcommand(/* min */ 0, /* max */ 1);
 

src/subcommand/checkout_subcommand.cpp

@@ -43,7 +43,7 @@ void checkout_subcommand::run()
     }
     else
     {
-        auto optional_commit = resolve_local_ref(repo, m_branch_name);
+        auto optional_commit = repo.resolve_local_ref(m_branch_name);
         if (!optional_commit)
         {
             // TODO: handle remote refs
@@ -56,26 +56,6 @@ void checkout_subcommand::run()
     }
 }
 
-std::optional<annotated_commit_wrapper> checkout_subcommand::resolve_local_ref
-(
-    const repository_wrapper& repo,
-    const std::string& target_name
-)
-{
-    if (auto ref = repo.find_reference_dwim(target_name))
-    {
-        return repo.find_annotated_commit(*ref);
-    }
-    else if (auto obj = repo.revparse_single(target_name))
-    {
-        return repo.find_annotated_commit(obj->oid());
-    }
-    else
-    {
-        return std::nullopt;
-    }
-}
-
 annotated_commit_wrapper checkout_subcommand::create_local_branch
 (
     repository_wrapper& repo,

src/subcommand/checkout_subcommand.hpp

@@ -17,12 +17,6 @@ class checkout_subcommand
 
 private:
 
-    std::optional<annotated_commit_wrapper> resolve_local_ref
-    (
-        const repository_wrapper& repo,
-        const std::string& target_name
-    );
-
     annotated_commit_wrapper create_local_branch
     (
         repository_wrapper& repo,

src/subcommand/commit_subcommand.cpp

@@ -32,5 +32,5 @@ void commit_subcommand::run()
         }
     }
 
-    repo.create_commit(author_committer_signatures, m_commit_message);
+    repo.create_commit(author_committer_signatures, m_commit_message, std::nullopt);
 }

src/subcommand/merge_subcommand.cpp

@@ -0,0 +1,100 @@
+#include <cassert>
+#include <git2/types.h>
+
+#include "merge_subcommand.hpp"
+// #include "../wrapper/repository_wrapper.hpp"
+
+
+merge_subcommand::merge_subcommand(const libgit2_object&, CLI::App& app)
+{
+    auto *sub = app.add_subcommand("merge", "Join two or more development histories together");
+
+    sub->add_option("<branch>", m_branches_to_merge, "Branch(es) to merge");
+
+    sub->callback([this]() { this->run(); });
+}
+
+annotated_commit_list_wrapper merge_subcommand::resolve_heads(const repository_wrapper& repo)
+{
+    std::vector<annotated_commit_wrapper> commits_to_merge;
+    commits_to_merge.reserve(m_branches_to_merge.size());
+
+    for (const auto branch_name:m_branches_to_merge)
+    {
+        std::optional<annotated_commit_wrapper> commit = repo.resolve_local_ref(branch_name);
+        if (commit.has_value())
+        {
+            commits_to_merge.push_back(std::move(commit).value());
+        }
+    }
+    return annotated_commit_list_wrapper(std::move(commits_to_merge));
+}
+
+void perform_fastforward(repository_wrapper& repo, const git_oid target_oid, int is_unborn)
+{
+    const git_checkout_options ff_checkout_options = GIT_CHECKOUT_OPTIONS_INIT;
+
+    auto lambda_get_target_ref = [] (auto repo, auto is_unborn)
+    {
+        if (!is_unborn)
+        {
+            return repo->head();
+        }
+        else
+        {
+            return repo->find_reference("HEAD");
+        }
+    };
+    reference_wrapper target_ref = lambda_get_target_ref(&repo, is_unborn);
+
+    object_wrapper target = repo.find_object(target_oid, GIT_OBJECT_COMMIT);
+
+    repo.checkout_tree(target, ff_checkout_options);
+
+    target_ref.write_new_ref(target_oid);
+}
+
+void merge_subcommand::run()
+{
+    auto directory = get_current_git_path();
+    auto bare = false;
+    auto repo = repository_wrapper::open(directory);
+
+    auto state = repo.state();
+    if (state != GIT_REPOSITORY_STATE_NONE)
+    {
+        std::cout << "repository is in unexpected state " << state <<std::endl;
+    }
+
+    git_merge_analysis_t analysis;
+	git_merge_preference_t preference;
+	annotated_commit_list_wrapper commits_to_merge = resolve_heads(repo);
+	size_t num_commits_to_merge = commits_to_merge.size();
+	git_annotated_commit** c_commits_to_merge = commits_to_merge;
+	auto commits_to_merge_const = const_cast<const git_annotated_commit**>(c_commits_to_merge);
+
+    throw_if_error(git_merge_analysis(&analysis, &preference, repo, commits_to_merge_const, num_commits_to_merge));
+
+    if (analysis & GIT_MERGE_ANALYSIS_UP_TO_DATE)
+    {
+        std::cout << "Already up-to-date" << std::endl;
+    }
+    else if (analysis & GIT_MERGE_ANALYSIS_UNBORN ||
+             (analysis & GIT_MERGE_ANALYSIS_FASTFORWARD &&
+             !(preference & GIT_MERGE_PREFERENCE_NO_FASTFORWARD)))
+    {
+        if (analysis & GIT_MERGE_ANALYSIS_UNBORN)
+        {
+            std::cout << "Unborn" << std::endl;
+        }
+        else
+        {
+            std::cout << "Fast-forward" << std::endl;
+        }
+        const annotated_commit_wrapper& commit = commits_to_merge.front();
+        const git_oid target_oid = commit.oid();
+        // Since this is a fast-forward, there can be only one merge head.
+        assert(num_commits_to_merge == 1);
+        perform_fastforward(repo, target_oid, (analysis & GIT_MERGE_ANALYSIS_UNBORN));
+    }
+}

src/subcommand/merge_subcommand.hpp

@@ -0,0 +1,20 @@
+#pragma once
+
+#include <CLI/CLI.hpp>
+
+#include "../utils/common.hpp"
+#include "../wrapper/repository_wrapper.hpp"
+
+class merge_subcommand
+{
+public:
+
+    explicit merge_subcommand(const libgit2_object&, CLI::App& app);
+    void run();
+
+private:
+
+    annotated_commit_list_wrapper resolve_heads(const repository_wrapper& repo);
+
+    std::vector<std::string> m_branches_to_merge;
+};

src/wrapper/annotated_commit_wrapper.hpp

@@ -27,3 +27,4 @@ class annotated_commit_wrapper : public wrapper_base<git_annotated_commit>
     friend class repository_wrapper;
 };
 
+using annotated_commit_list_wrapper = list_wrapper<annotated_commit_wrapper>;

src/wrapper/commit_wrapper.hpp

@@ -1,8 +1,9 @@
 #pragma once
 
 #include <git2.h>
+#include <vector>
+#include <string>
 
-#include "../wrapper/repository_wrapper.hpp"
 #include "../wrapper/wrapper_base.hpp"
 
 class commit_wrapper : public wrapper_base<git_commit>
@@ -28,3 +29,5 @@ class commit_wrapper : public wrapper_base<git_commit>
     friend class repository_wrapper;
     friend class reference_wrapper;
 };
+
+using commit_list_wrapper = list_wrapper<commit_wrapper>;

src/wrapper/refs_wrapper.cpp

@@ -1,4 +1,7 @@
 #include "../utils/git_exception.hpp"
+#include "object_wrapper.hpp"
+#include <git2/refs.h>
+#include <git2/types.h>
 #include "../wrapper/refs_wrapper.hpp"
 
 reference_wrapper::reference_wrapper(git_reference* ref)
@@ -21,3 +24,15 @@ bool reference_wrapper::is_remote() const
 {
     return git_reference_is_remote(*this);
 }
+
+const git_oid* reference_wrapper::target() const
+{
+    return git_reference_target(p_resource);
+}
+
+reference_wrapper reference_wrapper::write_new_ref(const git_oid target_oid)
+{
+    git_reference* new_ref;
+    throw_if_error(git_reference_set_target(&new_ref, p_resource, &target_oid, NULL));
+    return reference_wrapper(new_ref);
+}