nixos-install: add documentation for --channel, --no-channel-copy

nixos/doc/manual/man-nixos-install.xml

@@ -55,6 +55,13 @@
      <replaceable>path</replaceable>
    </arg>
 
+   <arg>
+     <arg choice='plain'>
+       <option>--channel</option>
+     </arg>
+     <replaceable>channel</replaceable>
+   </arg>
+
    <arg>
     <arg choice='plain'>
      <option>--no-channel-copy</option>
@@ -126,6 +133,12 @@
       specified in <filename>/mnt/etc/nixos/configuration.nix</filename>.
      </para>
     </listitem>
+    <listitem>
+      <para>
+        It installs the current channel <quote>nixos</quote> in the target channel
+        profile (unless <option>--no-channel-copy</option> is specified).
+      </para>
+    </listitem>
     <listitem>
      <para>
       It installs the GRUB boot loader on the device specified in the option
@@ -202,6 +215,18 @@
      </para>
     </listitem>
    </varlistentry>
+   <varlistentry>
+     <term>
+       <option>--channel</option>
+     </term>
+     <listitem>
+       <para>
+         If this option is provided, do not copy the current
+         <quote>nixos</quote> channel to the target host. Instead, use the
+         specified derivation.
+       </para>
+     </listitem>
+   </varlistentry>
    <varlistentry>
     <term>
      <option>-I</option>