* Refactoring.

* Convert tabs to spaces.

1 files changed, 176 insertions, 176 deletions

diff --git a/doc/manual/introduction.xml b/doc/manual/introduction.xml
index 5eea764592..feabeef9cd 100644
--- a/doc/manual/introduction.xml
+++ b/doc/manual/introduction.xml
@@ -15,74 +15,74 @@
       <title>Build management</title>
 
       <para>
-	Build management tools are used to perform <emphasis>software
-	  builds</emphasis>, that is, the construction of derived products
-	(<emphasis>derivates)</emphasis>) such as executable programs from
-	source code.  A commonly used build tool is Make, which is a standard
-	tool on Unix systems. These tools have to deal with several issues:
-	<itemizedlist>
-
-	  <listitem>
-	    <para>
-	      <emphasis>Efficiency</emphasis>.  Since building large systems
-	      can take a substantial amount of time, it is desirable that build
-	      steps that have been performed in the past are not repeated
-	      unnecessarily, i.e., if a new build differs from a previous build
-	      only with respect to certain sources, then only the build steps
-	      that (directly or indirectly) <emphasis>depend</emphasis> on
-	      those sources should be redone.
-	    </para>
-	  </listitem>
-
-	  <listitem>
-	    <para>
-	      <emphasis>Correctness</emphasis> is this context means that the
-	      derivates produced by a build are always consistent with the
-	      sources, that is, they are equal to what we would get if we were
-	      to build the derivates from those sources.  This requirement is
-	      trivially met when we do a full, unconditional build, but is far
-	      from trivial under the requirement of efficiency, since it is not
-	      easy to determine which derivates are affected by a change to a
-	      source.
-	    </para>
-	  </listitem>
-
-	  <listitem>
-	    <para>
-	      <emphasis>Variability</emphasis> is the property that a software
-	      system can be built in a (potentially large) number of variants.
-	      Variation exists both in <emphasis>time</emphasis>---the
-	      evolution of different versions of an artifact---and in
-	      <emphasis>space</emphasis>---the artifact might have
-	      configuration options that lead to variants that differ in the
-	      features they support (for example, a system might be built with
-	      or without debugging information).
-	    </para>
-
-	    <para>
-	      Build managers historically have had good support for variation
-	      in time (rebuilding the system in an intelligent way when sources
-	      change is one of the primary reasons to use a build manager), but
-	      not always for variation in space.  For example,
-	      <command>make</command> will not automatically ensure that
-	      variant builds are properly isolated from each other (they will
-	      in fact overwrite each other unless special precautions are
-	      taken).
-	    </para>
-	  </listitem>
-
-	  <listitem>
-	    <para>
-	      <emphasis>High-level system modelling language</emphasis>.  The
-	      language in which one describes what and how derivates are to be
-	      produced should have sufficient abstraction facilities to make it
-	      easy to specify the derivation of even very large systems.  Also,
-	      the language should be <emphasis>modular</emphasis> to enable
-	      components from possible different sources to be easily combined.
-	    </para>
-	  </listitem>
-
-	</itemizedlist>
+        Build management tools are used to perform <emphasis>software
+          builds</emphasis>, that is, the construction of derived products
+        (<emphasis>derivates)</emphasis>) such as executable programs from
+        source code.  A commonly used build tool is Make, which is a standard
+        tool on Unix systems. These tools have to deal with several issues:
+        <itemizedlist>
+
+          <listitem>
+            <para>
+              <emphasis>Efficiency</emphasis>.  Since building large systems
+              can take a substantial amount of time, it is desirable that build
+              steps that have been performed in the past are not repeated
+              unnecessarily, i.e., if a new build differs from a previous build
+              only with respect to certain sources, then only the build steps
+              that (directly or indirectly) <emphasis>depend</emphasis> on
+              those sources should be redone.
+            </para>
+          </listitem>
+
+          <listitem>
+            <para>
+              <emphasis>Correctness</emphasis> is this context means that the
+              derivates produced by a build are always consistent with the
+              sources, that is, they are equal to what we would get if we were
+              to build the derivates from those sources.  This requirement is
+              trivially met when we do a full, unconditional build, but is far
+              from trivial under the requirement of efficiency, since it is not
+              easy to determine which derivates are affected by a change to a
+              source.
+            </para>
+          </listitem>
+
+          <listitem>
+            <para>
+              <emphasis>Variability</emphasis> is the property that a software
+              system can be built in a (potentially large) number of variants.
+              Variation exists both in <emphasis>time</emphasis>---the
+              evolution of different versions of an artifact---and in
+              <emphasis>space</emphasis>---the artifact might have
+              configuration options that lead to variants that differ in the
+              features they support (for example, a system might be built with
+              or without debugging information).
+            </para>
+
+            <para>
+              Build managers historically have had good support for variation
+              in time (rebuilding the system in an intelligent way when sources
+              change is one of the primary reasons to use a build manager), but
+              not always for variation in space.  For example,
+              <command>make</command> will not automatically ensure that
+              variant builds are properly isolated from each other (they will
+              in fact overwrite each other unless special precautions are
+              taken).
+            </para>
+          </listitem>
+
+          <listitem>
+            <para>
+              <emphasis>High-level system modelling language</emphasis>.  The
+              language in which one describes what and how derivates are to be
+              produced should have sufficient abstraction facilities to make it
+              easy to specify the derivation of even very large systems.  Also,
+              the language should be <emphasis>modular</emphasis> to enable
+              components from possible different sources to be easily combined.
+            </para>
+          </listitem>
+
+        </itemizedlist>
       </para>
 
     </sect2>
@@ -91,33 +91,33 @@
       <title>Package management</title>
 
       <para>
-	After software has been built, is must also be
-	<emphasis>deployed</emphasis> in the intended target environment, e.g.,
-	the user's workstation.  Examples include the Red Hat package manager
-	(RPM), Microsoft's MSI, and so on.  Here also we have several issues to
-	contend with:
-	<itemizedlist>
-	  <listitem>
-	    <para>
-	      The <emphasis>creation</emphasis> of packages from some formal
-	      description of what artifacts should be distributed in the
-	      package.
-	    </para>
-	  </listitem>
-	  <listitem>
-	    <para>
-	      The <emphasis>deployment</emphasis> of packages, that is, the
-	      mechanism by which we get them onto the intended target
-	      environment.  This can be as simple as copying a file, but
-	      complexity comes from the wide range of possible installation
-	      media (such as a network install), and the scalability of the
-	      process (if a program must be installed on a thousand systems, we
-	      do not want to visit each system and perform some manual steps to
-	      install the program on that system; that is, the complexity for
-	      the system administrator should be constant, not linear).
-	    </para>
-	  </listitem>
-	</itemizedlist>
+        After software has been built, is must also be
+        <emphasis>deployed</emphasis> in the intended target environment, e.g.,
+        the user's workstation.  Examples include the Red Hat package manager
+        (RPM), Microsoft's MSI, and so on.  Here also we have several issues to
+        contend with:
+        <itemizedlist>
+          <listitem>
+            <para>
+              The <emphasis>creation</emphasis> of packages from some formal
+              description of what artifacts should be distributed in the
+              package.
+            </para>
+          </listitem>
+          <listitem>
+            <para>
+              The <emphasis>deployment</emphasis> of packages, that is, the
+              mechanism by which we get them onto the intended target
+              environment.  This can be as simple as copying a file, but
+              complexity comes from the wide range of possible installation
+              media (such as a network install), and the scalability of the
+              process (if a program must be installed on a thousand systems, we
+              do not want to visit each system and perform some manual steps to
+              install the program on that system; that is, the complexity for
+              the system administrator should be constant, not linear).
+            </para>
+          </listitem>
+        </itemizedlist>
       </para>
     </sect2>
 
@@ -136,95 +136,95 @@
     <itemizedlist>
 
       <listitem>
-	<para>
-	  <emphasis>Reliable dependencies.</emphasis>  Builds of file system
-	  objects depend on other file system object, such as source files,
-	  tools, and so on.  We would like to ensure that a build does not
-	  refer to any objects that have not been declared as inputs for that
-	  build.  This is important for several reasons.  First, if any of the
-	  inputs change, we need to rebuild the things that depend on them to
-	  maintain consistency between sources and derivates.  Second, when we
-	  <emphasis>deploy</emphasis> file system objects (that is, copy them
-	  to a different system), we want to be certain that we copy everything
-	  that we need.
-	</para>
-
-	<para>
-	  Nix ensures this by building and storing file system objects in paths
-	  that are infeasible to predict in advance.  For example, the
-	  artifacts of a package <literal>X</literal> might be stored in
-	  <filename>/nix/store/d58a0606ed616820de291d594602665d-X</filename>,
-	  rather than in, say, <filename>/usr/lib</filename>.  The path
-	  component <filename>d58a...</filename> is actually a cryptographic
-	  hash of all the inputs (i.e., sources, requisites, and build flags)
-	  used in building <literal>X</literal>, and as such is very fragile:
-	  any change to the inputs will change the hash.  Therefore it is not
-	  sensible to <emphasis>hard-code</emphasis> such a path into the build
-	  scripts of a package <literal>Y</literal> that uses
-	  <literal>X</literal> (as does happen with <quote>fixed</quote> paths
-	  such as <filename>/usr/lib</filename>).  Rather, the build script of
-	  package <literal>Y</literal> is parameterised with the actual
-	  location of <literal>X</literal>, which is supplied by the Nix
-	  system.
-	</para>
+        <para>
+          <emphasis>Reliable dependencies.</emphasis>  Builds of file system
+          objects depend on other file system object, such as source files,
+          tools, and so on.  We would like to ensure that a build does not
+          refer to any objects that have not been declared as inputs for that
+          build.  This is important for several reasons.  First, if any of the
+          inputs change, we need to rebuild the things that depend on them to
+          maintain consistency between sources and derivates.  Second, when we
+          <emphasis>deploy</emphasis> file system objects (that is, copy them
+          to a different system), we want to be certain that we copy everything
+          that we need.
+        </para>
+
+        <para>
+          Nix ensures this by building and storing file system objects in paths
+          that are infeasible to predict in advance.  For example, the
+          artifacts of a package <literal>X</literal> might be stored in
+          <filename>/nix/store/d58a0606ed616820de291d594602665d-X</filename>,
+          rather than in, say, <filename>/usr/lib</filename>.  The path
+          component <filename>d58a...</filename> is actually a cryptographic
+          hash of all the inputs (i.e., sources, requisites, and build flags)
+          used in building <literal>X</literal>, and as such is very fragile:
+          any change to the inputs will change the hash.  Therefore it is not
+          sensible to <emphasis>hard-code</emphasis> such a path into the build
+          scripts of a package <literal>Y</literal> that uses
+          <literal>X</literal> (as does happen with <quote>fixed</quote> paths
+          such as <filename>/usr/lib</filename>).  Rather, the build script of
+          package <literal>Y</literal> is parameterised with the actual
+          location of <literal>X</literal>, which is supplied by the Nix
+          system.
+        </para>
       </listitem>
 
       <listitem>
-	<para>
-	  <emphasis>Support for variability.</emphasis>  
-	</para>
-	
-	<para>
-	  As stated above, the path name of a file system object contain a
-	  cryptographic hash of all inputs involved in building it.  A change to
-	  any of the inputs will cause the hash to change--and by extension,
-	  the path name.  These inputs include both sources (variation in time)
-	  and configuration options (variation in space).  Therefore variants
-	  of the same package don't clash---they can co-exist peacefully within
-	  the same file system.  So thanks to Nix's mechanism for reliably
-	  dealing with dependencies, we obtain management of variants for free
-	  (or, to quote Simon Peyton-Jone, it's not free, but it has already
-	  been paid for).
-	</para>
+        <para>
+          <emphasis>Support for variability.</emphasis>  
+        </para>
+        
+        <para>
+          As stated above, the path name of a file system object contain a
+          cryptographic hash of all inputs involved in building it.  A change to
+          any of the inputs will cause the hash to change--and by extension,
+          the path name.  These inputs include both sources (variation in time)
+          and configuration options (variation in space).  Therefore variants
+          of the same package don't clash---they can co-exist peacefully within
+          the same file system.  So thanks to Nix's mechanism for reliably
+          dealing with dependencies, we obtain management of variants for free
+          (or, to quote Simon Peyton-Jone, it's not free, but it has already
+          been paid for).
+        </para>
 
       </listitem>
 
       <listitem>
-	<para>
-	  <emphasis>Transparent source/binary deployment.</emphasis>
-	</para>
+        <para>
+          <emphasis>Transparent source/binary deployment.</emphasis>
+        </para>
       </listitem>
 
       <listitem>
-	<para>
-	  <emphasis>Easy configuration duplication.</emphasis>
-	</para>
+        <para>
+          <emphasis>Easy configuration duplication.</emphasis>
+        </para>
       </listitem>
 
       <listitem>
-	<para>
-	  <emphasis>Automatic storage management.</emphasis>
-	</para>
+        <para>
+          <emphasis>Automatic storage management.</emphasis>
+        </para>
       </listitem>
 
       <listitem>
-	<para>
-	  <emphasis>Atomic upgrades and rollbacks.</emphasis>
-	</para>
+        <para>
+          <emphasis>Atomic upgrades and rollbacks.</emphasis>
+        </para>
       </listitem>
 
       <listitem>
-	<para>
-	  <emphasis>Support for many simultaneous configurations.</emphasis>
-	</para>
+        <para>
+          <emphasis>Support for many simultaneous configurations.</emphasis>
+        </para>
       </listitem>
 
       <listitem>
-	<para>
-	  <emphasis>Portability.</emphasis>  Nix is quite portable.  Contrary
-	  to build systems like those in, e.g., Vesta and ClearCase [sic?], it
-	  does not rely on operating system extensions.
-	</para>
+        <para>
+          <emphasis>Portability.</emphasis>  Nix is quite portable.  Contrary
+          to build systems like those in, e.g., Vesta and ClearCase [sic?], it
+          does not rely on operating system extensions.
+        </para>
       </listitem>
 
     </itemizedlist>
@@ -236,20 +236,20 @@
     <itemizedlist>
 
       <listitem>
-	<para>
-	  <emphasis>Build management.</emphasis>  In principle it is already
-	  possible to do build management using Fix (by writing builders that
-	  perform appropriate build steps), but the Fix language is not yet
-	  powerful enough to make this pleasant.  The <ulink
-	    url='http://www.cs.uu.nl/~eelco/maak/'>Maak build manager</ulink>
-	  should be retargeted to produce Nix expressions, or alternatively,
-	  extend Fix with Maak's semantics and concrete syntax (since Fix needs
-	  a concrete syntax anyway).  Another interesting idea is to write a
-	  <command>make</command> implementation that uses Nix as a back-end to
-	  support <ulink
-	    url='http://www.research.att.com/~bs/bs_faq.html#legacy'>legacy</ulink> 
-	  build files.
-	</para>
+        <para>
+          <emphasis>Build management.</emphasis>  In principle it is already
+          possible to do build management using Fix (by writing builders that
+          perform appropriate build steps), but the Fix language is not yet
+          powerful enough to make this pleasant.  The <ulink
+            url='http://www.cs.uu.nl/~eelco/maak/'>Maak build manager</ulink>
+          should be retargeted to produce Nix expressions, or alternatively,
+          extend Fix with Maak's semantics and concrete syntax (since Fix needs
+          a concrete syntax anyway).  Another interesting idea is to write a
+          <command>make</command> implementation that uses Nix as a back-end to
+          support <ulink
+            url='http://www.research.att.com/~bs/bs_faq.html#legacy'>legacy</ulink> 
+          build files.
+        </para>
       </listitem>
 
     </itemizedlist>