support renaming buffers

Changing buffer name allows to save a *make* or *grep* buffer when
launching another one for exemple.

README.asciidoc

@@ -254,7 +254,8 @@ Commands are entered using +:+.
  * +source <filename>+: execute commands in <filename>
  * +runtime <filename>+: execute commands in <filename>, <filename>
       is relative to kak executable path.
- * +name <name>+: set current client name
+ * +nameclient <name>+: set current client name
+ * +namebuf <name>+: set current buffer name
  * +exec [-client <name>] <keys>+: execute <keys> as if pressed in normal mode.
       if client if specified, exec keys in the named client context.
  * +eval [-client <name>] <command>+: execute <command> as if entered in command line

src/buffer.cc

@@ -72,6 +72,20 @@ String Buffer::display_name() const
     return m_name;
 }
 
+bool Buffer::set_name(String name)
+{
+    Buffer* other = BufferManager::instance().get_buffer_ifp(name);
+    if (other == nullptr or other == this)
+    {
+        if (m_flags & Flags::File)
+            m_name = real_path(name);
+        else
+            m_name = std::move(name);
+        return true;
+    }
+    return false;
+}
+
 BufferIterator Buffer::iterator_at(const BufferCoord& line_and_column,
                                    bool avoid_eol) const
 {

src/buffer.hh

@@ -109,6 +109,8 @@ public:
     Flags flags() const { return m_flags; }
     Flags& flags() { return m_flags; }
 
+    bool set_name(String name);
+
     void insert(BufferIterator pos, String content);
     void erase(BufferIterator begin, BufferIterator end);
 

src/commands.cc

@@ -240,6 +240,14 @@ void delete_buffer(const CommandParameters& params, Context& context)
     manager.delete_buffer(buffer);
 }
 
+void set_buffer_name(const CommandParameters& params, Context& context)
+{
+    ParametersParser parser(params, OptionMap{},
+                            ParametersParser::Flags::None, 1, 1);
+    if (not context.buffer().set_name(parser[0]))
+        throw runtime_error("unable to change buffer name to " + parser[0]);
+}
+
 template<typename Group>
 Group& get_group(Group& root, const String& group_path)
 {
@@ -900,6 +908,7 @@ void register_commands()
     cm.register_commands({ "b", "buffer" }, show_buffer, buffer_completer);
     cm.register_commands({ "db", "delbuf" }, delete_buffer<false>, buffer_completer);
     cm.register_commands({ "db!", "delbuf!" }, delete_buffer<true>, buffer_completer);
+    cm.register_commands({"nb", "namebuf"}, set_buffer_name);
 
     auto get_highlighters = [](const Context& c) -> HighlighterGroup& { return c.window().highlighters(); };
     auto get_filters      = [](const Context& c) -> FilterGroup& { return c.window().filters(); };
@@ -943,7 +952,7 @@ void register_commands()
                          }));
 
     cm.register_commands({"ca", "colalias"}, define_color_alias);
-    cm.register_commands({"name"}, set_client_name);
+    cm.register_commands({"nc", "nameclient"}, set_client_name);
 
     cm.register_command("cd", change_working_directory, filename_completer);
 }