command: added command "decoders"

This command prints a list of decoder plugins and their suffixes /
MIME types.

Makefile.am

@@ -81,6 +81,7 @@ mpd_headers = \
 	src/dirvec.h \
 	src/gcc.h \
 	src/decoder_list.h \
+	src/decoder_print.h \
 	src/decoder/_flac_common.h \
 	src/decoder/_ogg_common.h \
 	src/input_plugin.h \
@@ -212,6 +213,7 @@ src_mpd_SOURCES = \
 	src/decoder_control.c \
 	src/decoder_api.c \
 	src/decoder_internal.c \
+	src/decoder_print.c \
 	src/directory.c \
 	src/directory_save.c \
 	src/directory_print.c \

doc/protocol.xml

@@ -1589,6 +1589,25 @@ OK
             </para>
           </listitem>
         </varlistentry>
+        <varlistentry id="command_decoders">
+          <term>
+            <cmdsynopsis>
+              <command>decoders</command>
+            </cmdsynopsis>
+          </term>
+          <listitem>
+            <para>
+              Print a list of decoder plugins, followed by their
+              supported suffixes and MIME types.  Example response:
+            </para>
+            <programlisting>plugin: mad
+suffix: mp3
+suffix: mp2
+mime_type: audio/mpeg
+plugin: mpcdec
+suffix: mpc</programlisting>
+          </listitem>
+        </varlistentry>
       </variablelist>
     </section>
   </chapter>

src/command.c

@@ -26,6 +26,7 @@
 #include "queue_print.h"
 #include "ls.h"
 #include "uri.h"
+#include "decoder_print.h"
 #include "directory.h"
 #include "directory_print.h"
 #include "database.h"
@@ -388,6 +389,14 @@ handle_urlhandlers(struct client *client,
 	return COMMAND_RETURN_OK;
 }
 
+static enum command_return
+handle_decoders(struct client *client,
+		G_GNUC_UNUSED int argc, G_GNUC_UNUSED char *argv[])
+{
+	decoder_list_print(client);
+	return COMMAND_RETURN_OK;
+}
+
 static enum command_return
 handle_tagtypes(struct client *client,
 		G_GNUC_UNUSED int argc, G_GNUC_UNUSED char *argv[])
@@ -1755,6 +1764,7 @@ static const struct command commands[] = {
 	{ "count", PERMISSION_READ, 2, -1, handle_count },
 	{ "crossfade", PERMISSION_CONTROL, 1, 1, handle_crossfade },
 	{ "currentsong", PERMISSION_READ, 0, 0, handle_currentsong },
+	{ "decoders", PERMISSION_READ, 0, 0, handle_decoders },
 	{ "delete", PERMISSION_CONTROL, 1, 1, handle_delete },
 	{ "deleteid", PERMISSION_CONTROL, 1, 1, handle_deleteid },
 	{ "disableoutput", PERMISSION_ADMIN, 1, 1, handle_disableoutput },