Add support for echo -quoting (raw|kakoune|shell) switch

doc/pages/commands.asciidoc

@@ -210,6 +210,20 @@ of the file onto the filesystem
         write the given text to the given file on the host
         filesystem.
 
+    *-quoting* <quoting>:::
+        define how each arguments are quoted in echo output:
+
+        - *raw* (default)::::
+            just join each argument with a space
+
+        - *kakoune*::::
+            also wrap each argument in single quotes, doubling-up
+            embedded quotes.
+
+        - *shell*::::
+            also wrap each arguments in single quotes and escape
+            embedded quotes in a shell compatible way.
+
 *set-face* <scope> <name> <facespec>::
     *alias* face +
     define a face in *scope*

src/commands.cc

@@ -1245,6 +1245,7 @@ const CommandDesc echo_cmd = {
     "echo <params>...: display given parameters in the status line",
     ParameterDesc{
         { { "markup", { false, "parse markup" } },
+          { "quoting", { true, "quote each argument separately using the given style (raw|kakoune|shell)" } },
           { "to-file", { true, "echo contents to given filename" } },
           { "debug", { false, "write to debug buffer instead of status line" } } },
         ParameterDesc::Flags::SwitchesOnlyAtStart
@@ -1254,7 +1255,13 @@ const CommandDesc echo_cmd = {
     CommandCompleter{},
     [](const ParametersParser& parser, Context& context, const ShellContext&)
     {
-        String message = join(parser, ' ', false);
+        String message;
+        if (auto quoting = parser.get_switch("quoting"))
+            message = join(parser | transform(quoter(option_from_string(Meta::Type<Quoting>{}, *quoting))),
+                           ' ', false);
+        else
+            message = join(parser, ' ', false);
+
         if (auto filename = parser.get_switch("to-file"))
             return write_to_file(*filename, message);
 

src/string_utils.hh

@@ -2,6 +2,7 @@
 #define string_utils_hh_INCLUDED
 
 #include "string.hh"
+#include "enum.hh"
 #include "vector.hh"
 #include "optional.hh"
 
@@ -143,6 +144,15 @@ enum class Quoting
     Shell
 };
 
+constexpr auto enum_desc(Meta::Type<Quoting>)
+{
+    return make_array<EnumDesc<Quoting>, 3>({
+        { Quoting::Raw, "raw" },
+        { Quoting::Kakoune, "kakoune" },
+        { Quoting::Shell, "shell" }
+    });
+}
+
 inline auto quoter(Quoting quoting)
 {
     switch (quoting)