Make register expansions expand to the full register content

Now that we have a nice standard way to express lists of strings,
registers can be fully exposed. An new $kak_main_reg_... env var
was added to provide the previous behaviour which is relied on by
doc.kak.

doc/pages/expansions.asciidoc

@@ -38,8 +38,8 @@ parameter:
     section)
 
 *reg*::
-    register expansion, will expand to the content of the register named
-    by *<content>*. See <<registers#,`:doc registers`>>
+    register expansion, will expand to the strings stored in the register
+    named by *<content>*. See <<registers#,`:doc registers`>>
 
 *opt*::
     option expansion, will expand to the value of the option named by
@@ -114,7 +114,10 @@ informations about Kakoune's state:
     value of option *name*
 
 *kak_reg_<r>*::
-    value of register *r*
+    quoted list of value of register *r*
+
+*kak_main_reg_<r>*::
+    content of register *r* associated with the main selection.
 
 *kak_session*::
     name of the current session

rc/base/autowrap.kak

@@ -31,7 +31,7 @@ define-command -hidden autowrap-cursor %{ evaluate-commands -save-regs '/"|^@m'
                             execute-keys '<a-]>p<a-x><a-j>|${format_cmd}<ret>'
                             try %{ execute-keys s\h+$<ret> d }
                         }
-                        select '${kak_reg_m}'
+                        select '${kak_main_reg_m}'
                     "
                 fi
             }

rc/core/doc.kak

@@ -41,7 +41,7 @@ define-command -hidden doc-parse-anchors %{
         # Find sections as add them as imlicit anchors
         execute-keys \%s ^={2,}\h+([^\n]+)$ <ret>
         evaluate-commands -itersel %{
-            set-option -add buffer doc_anchors "%val{selection_desc}|%sh{printf '%s' ""$kak_reg_1"" | tr '[A-Z ]' '[a-z-]'}"
+            set-option -add buffer doc_anchors "%val{selection_desc}|%sh{printf '%s' ""$kak_main_reg_1"" | tr '[A-Z ]' '[a-z-]'}"
         }
 
         # Parse explicit anchors and remove their text

src/command_manager.cc

@@ -263,6 +263,16 @@ auto expand_option(Option& opt, std::false_type)
     return opt.get_as_strings();
 }
 
+auto expand_register(StringView reg, const Context& context, std::true_type)
+{
+    return join(RegisterManager::instance()[reg].get(context) | transform(quote), ' ', false);
+}
+
+auto expand_register(StringView reg, const Context& context, std::false_type)
+{
+    return RegisterManager::instance()[reg].get(context) | gather<Vector<String>>();
+}
+
 String expand_arobase(ConstArrayView<String> params, std::true_type)
 {
     return join(params, ' ', false);
@@ -298,7 +308,7 @@ expand_token(const Token& token, const Context& context, const ShellContext& she
         return {str};
     }
     case Token::Type::RegisterExpand:
-        return {context.main_sel_register_value(content).str()};
+        return expand_register(content, context, IsSingle{});
     case Token::Type::OptionExpand:
         return expand_option(context.options()[content], IsSingle{});
     case Token::Type::ValExpand:

src/main.cc

@@ -132,10 +132,14 @@ static const EnvVarDesc builtin_env_vars[] = { {
         "opt_", true,
         [](StringView name, const Context& context)
         { return context.options()[name.substr(4_byte)].get_as_string(); }
+    }, {
+        "main_reg_", true,
+        [](StringView name, const Context& context)
+        { return context.main_sel_register_value(name.substr(9_byte)).str(); }
     }, {
         "reg_", true,
         [](StringView name, const Context& context)
-        { return context.main_sel_register_value(name.substr(4_byte)).str(); }
+        { return join(RegisterManager::instance()[name.substr(4_byte)].get(context) | transform(quote), ' ', false); }
     }, {
         "client_env_", true,
         [](StringView name, const Context& context)