address review comments

Author: SandrineP

src/subcommand/commit_subcommand.cpp

@@ -10,6 +10,8 @@ commit_subcommand::commit_subcommand(const libgit2_object&, CLI::App& app)
 {
     auto *sub = app.add_subcommand("commit", "Record changes to the repository");
 
+    // TODO: merge the following option and flag into: sub->add_option("-m,--message", m_commit_message, "Commit message")
+    // when we have a solution to ask for a message when not using the -m flag.
     sub->add_option("commit_message", m_commit_message, "Commit message");
 
     sub->add_flag("-m,--message", m_commit_message_flag, "");
@@ -23,12 +25,16 @@ void commit_subcommand::run()
     auto directory = get_current_git_path();
     auto bare = false;
     auto repo = repository_wrapper::init(directory, bare);
-    auto author_committer_signatures =  signature_wrapper::get_default_signature_from_env(repo);
+    auto author_committer_signatures = signature_wrapper::get_default_signature_from_env(repo);
 
     if (!m_commit_message_flag)
     {
         throw std::runtime_error("Please provide a message using the -m flag.");
     }
+    if (m_commit_message.empty())
+    {
+        throw std::runtime_error("Please provide a commit message.");
+    }
 
     repo.create_commit(author_committer_signatures, m_commit_message);
 }