* nix-build: default to `./default.nix' if no paths are specified.

So when using Nix as a build tool, you can just say `nix-build' and
  it will build the top-level derivation defined in `default.nix'.

doc/manual/nix-build.xml

@@ -25,6 +25,10 @@ to multiple derivations, multiple sequentially numbered symlinks are
 created (<filename>result</filename>, <filename>result-2</filename>,
 and so on).</para>
 
+<para>If no <replaceable>paths</replaceable> are specified, then
+<command>nix-build</command> will use <filename>default.nix</filename>
+in the current directory, if it exists.</para>
+
 <note><para><command>nix-build</command> is essentially a wrapper
 around <link
 linkend="sec-nix-instantiate"><command>nix-instantiate</command></link>

doc/manual/package-management.xml

@@ -176,7 +176,7 @@ set.</para></footnote></para>
 <sect1 id="sec-profiles"><title>Profiles</title>
 
 <para>Profiles and user environments are Nix’s mechanism for
-implementing the ability to allow differens users to have different
+implementing the ability to allow different users to have different
 configurations, and to do atomic upgrades and rollbacks.  To
 understand how they work, it’s useful to know a bit about how Nix
 works.  In Nix, components are stored in unique locations in the