[dnf5] Implement new argument "--show-new-leaves"

Shows newly installed leaf packages and packages that became leaves
after a transaction.

dnf5/include/dnf5/context.hpp

@@ -114,6 +114,11 @@ class Context : public libdnf5::cli::session::Session {
 
     bool get_dump_variables() const { return dump_variables; }
 
+    /// Set to true to show newly installed leaf packages and packages that became leaves after a transaction.
+    void set_show_new_leaves(bool show_new_leaves) { this->show_new_leaves = show_new_leaves; }
+
+    bool get_show_new_leaves() const { return show_new_leaves; }
+
     Plugins & get_plugins() { return *plugins; }
 
     libdnf5::Goal * get_goal(bool new_if_not_exist = true);
@@ -145,6 +150,7 @@ class Context : public libdnf5::cli::session::Session {
     bool dump_main_config{false};
     std::vector<std::string> dump_repo_config_id_list;
     bool dump_variables{false};
+    bool show_new_leaves{false};
 
     std::unique_ptr<Plugins> plugins;
     std::unique_ptr<libdnf5::Goal> goal;

dnf5/main.cpp

@@ -61,6 +61,7 @@ along with libdnf.  If not, see <https://www.gnu.org/licenses/>.
 #include <libdnf5/logger/global_logger.hpp>
 #include <libdnf5/logger/memory_buffer_logger.hpp>
 #include <libdnf5/repo/repo_cache.hpp>
+#include <libdnf5/rpm/package_query.hpp>
 #include <libdnf5/utils/bgettext/bgettext-mark-domain.h>
 #include <libdnf5/version.hpp>
 #include <string.h>
@@ -498,6 +499,21 @@ void RootCommand::set_argument_parser() {
         });
     global_options_group->register_argument(releasever);
 
+    {
+        auto show_new_leaves = parser.add_new_named_arg("show-new-leaves");
+        show_new_leaves->set_long_name("show-new-leaves");
+        show_new_leaves->set_description(
+            "Show newly installed leaf packages and packages that became leaves after a transaction.");
+        show_new_leaves->set_parse_hook_func([&ctx](
+                                                 [[maybe_unused]] ArgumentParser::NamedArg * arg,
+                                                 [[maybe_unused]] const char * option,
+                                                 [[maybe_unused]] const char * value) {
+            ctx.set_show_new_leaves(true);
+            return true;
+        });
+        global_options_group->register_argument(show_new_leaves);
+    }
+
     {
         auto debug_solver = parser.add_new_named_arg("debug_solver");
         debug_solver->set_long_name("debugsolver");
@@ -825,6 +841,47 @@ static void dump_variables(Context & context) {
     }
 }
 
+static void print_new_leaves(Context & context) {
+    libdnf5::rpm::PackageQuery pkg_query(context.base);
+    pkg_query.filter_installed();
+    libdnf5::rpm::PackageQuery pre_trans_leaves_query(pkg_query);
+    pre_trans_leaves_query.filter_leaves();
+
+    // Calculate the new system state (list of installed packages) after a successful transaction.
+    // Current state plus inbound minus outbound packages.
+    for (const auto & trans_pkg : context.get_transaction()->get_transaction_packages()) {
+        if (libdnf5::transaction::transaction_item_action_is_inbound(trans_pkg.get_action())) {
+            pkg_query.add(trans_pkg.get_package());
+        } else if (libdnf5::transaction::transaction_item_action_is_outbound(trans_pkg.get_action())) {
+            pkg_query.remove(trans_pkg.get_package());
+        }
+    }
+
+    pkg_query.filter_leaves();
+    pkg_query.difference(pre_trans_leaves_query);
+
+    std::set<std::string> pre_trans_leaves_na;
+    std::set<std::string> new_leaves_na;
+    for (const auto & package : pre_trans_leaves_query) {
+        pre_trans_leaves_na.insert(package.get_na());
+    }
+    for (const auto & package : pkg_query) {
+        auto na = package.get_na();
+        // Filters out new leaves packages with the same name and architecture as previously existing leaves.
+        if (!pre_trans_leaves_na.contains(na)) {
+            new_leaves_na.insert(package.get_na());
+        }
+    }
+
+    if (!new_leaves_na.empty()) {
+        std::cout << "New leaves:" << std::endl;
+        for (const auto & leaf_pkg : new_leaves_na) {
+            std::cout << " " << leaf_pkg << std::endl;
+        }
+        std::cout << std::endl;
+    }
+}
+
 }  // namespace dnf5
 
 
@@ -992,6 +1049,10 @@ int main(int argc, char * argv[]) try {
                     return static_cast<int>(libdnf5::cli::ExitCode::SUCCESS);
                 }
 
+                if (context.get_show_new_leaves()) {
+                    dnf5::print_new_leaves(context);
+                }
+
                 dnf5::print_transaction_size_stats(context);
 
                 if (base.get_config().get_downloadonly_option().get_value()) {

doc/dnf5.8.rst

@@ -253,6 +253,9 @@ Following options are applicable in the general context for any ``dnf5`` command
 ``--setvar=VAR_NAME=VALUE``
     | Override a ``DNF5`` variable value, like ``arch``, ``releasever``, etc.
 
+``--show-new-leaves``
+    | Show newly installed leaf packages and packages that became leaves after a transaction.
+
 ``--skip-broken``
     | Resolve any dependency problems by removing packages that are causing problems from the transaction.