Add a -verbatim switch to evaluate-commands for perfect forwarding

-verbatim will disable argument parsing in evaluate-commands, making
it possible to forward a single command to a different context without
triggering a reparsing of the arguments.

Fixes -try-client support in grep.kak

Closes #3153

doc/pages/changelog.asciidoc

@@ -12,6 +12,9 @@ released versions.
   `InsertBegin`, `InsertEnd`, `NormalBegin` and `NormalEnd`
   were removed.
 
+* `-verbatim` switch in `evaluate-commands` for perfect command
+  forwarding to another context.
+
 == Kakoune 2019.07.01
 
 * Re-organized bundled script files directory hierarchy.

doc/pages/execeval.asciidoc

@@ -55,6 +55,10 @@ when the commands have been executed: */*, *"*, *|*, *^*, *@*.
     disable hook execution while executing the keys/commands
     (See <<hooks#disabling-hooks,`:doc hooks`>>)
 
+*-verbatim*::
+    do not reparse and split positional arguments. Forward them
+    exactly as given to the `evaluate-commands` command.
+
 == execute-keys specific switches
 
 *-with-maps*::

rc/tools/grep.kak

@@ -44,7 +44,7 @@ define-command -hidden grep-jump %{
         try %{
             execute-keys '<a-x>s^((?:\w:)?[^:]+):(\d+):(\d+)?<ret>'
             set-option buffer grep_current_line %val{cursor_line}
-            evaluate-commands -try-client %opt{jumpclient} %{ edit -existing %reg{1} %reg{2} %reg{3} }
+            evaluate-commands -try-client %opt{jumpclient} -verbatim -- edit -existing %reg{1} %reg{2} %reg{3}
             try %{ focus %opt{jumpclient} }
         }
     }

src/command_manager.hh

@@ -100,6 +100,12 @@ public:
     void execute(StringView command_line, Context& context,
                  const ShellContext& shell_context = ShellContext{});
 
+    void execute_single_command(CommandParameters params,
+                                Context& context,
+                                const ShellContext& shell_context,
+                                BufferCoord pos = {});
+
+
     Completions complete(const Context& context, CompletionFlags flags,
                          StringView command_line, ByteCount cursor_pos);
 
@@ -132,11 +138,6 @@ public:
     Completions complete_module_name(StringView query) const;
 
 private:
-    void execute_single_command(CommandParameters params,
-                                Context& context,
-                                const ShellContext& shell_context,
-                                BufferCoord pos);
-
     struct Command
     {
         CommandFunc func;

src/commands.cc

@@ -1910,7 +1910,10 @@ const CommandDesc eval_string_cmd = {
     "evaluate-commands",
     "eval",
     "evaluate-commands [<switches>] <commands>...: execute commands as if entered by user",
-    make_context_wrap_params<1>({{{"no-hooks", { false, "disable hooks while executing commands" }}}}),
+    make_context_wrap_params<2>({{
+        {"no-hooks", { false, "disable hooks while executing commands" }},
+        {"verbatim", { false, "do not reparse argument" }}
+    }}),
     CommandFlags::None,
     CommandHelper{},
     CommandCompleter{},
@@ -1920,7 +1923,10 @@ const CommandDesc eval_string_cmd = {
             const bool no_hooks = context.hooks_disabled() or parser.get_switch("no-hooks");
             ScopedSetBool disable_hoooks(context.hooks_disabled(), no_hooks);
 
-            CommandManager::instance().execute(join(parser, ' ', false), context, shell_context);
+            if (parser.get_switch("verbatim"))
+                CommandManager::instance().execute_single_command(parser | gather<Vector>(), context, shell_context);
+            else
+                CommandManager::instance().execute(join(parser, ' ', false), context, shell_context);
         });
     }
 };