Add cross-references

doc/sparse.texi

@@ -3,6 +3,8 @@
 @c This file is distributed under GFDL 1.1 or any later version
 @c published by the Free Software Foundation.
 
+@cindex sparse formats
+@cindex sparse versions
 The notion of sparse file, and the ways of handling it from the point
 of view of @GNUTAR{} user have been described in detail in
 @ref{sparse}.  This chapter describes the internal format @GNUTAR{}
@@ -33,6 +35,8 @@ The following subsections describe each format in detail.
 @node Old GNU Format
 @appendixsubsec Old GNU Format
 
+@cindex sparse formats, Old GNU
+@cindex Old GNU sparse format
 The format introduced some time around 1990 (v. 1.09).  It was
 designed on top of standard @code{ustar} headers in such an
 unfortunate way that some of its fields overwrote fields required by
@@ -83,24 +87,28 @@ A header with @code{isextended=0} ends the map.
 
 @node PAX 0
 @appendixsubsec PAX Format, Versions 0.0 and 0.1
-@UNREVISED{}
 
+@cindex sparse formats, v.0.0
 There are two formats available in this branch.  The version @code{0.0}
 is the initial version of sparse format used by @command{tar}
 versions 1.14--1.15.1.  The sparse file map is kept in extended
 (@code{x}) PAX header variables:
 
 @table @code
+@vrindex GNU.sparse.size, extended header variable
 @item GNU.sparse.size
 Real size of the stored file
 
 @item GNU.sparse.numblocks
+@vrindex GNU.sparse.numblocks, extended header variable
 Number of blocks in the sparse map
 
 @item GNU.sparse.offset
+@vrindex GNU.sparse.offset, extended header variable
 Offset of the data block
 
 @item GNU.sparse.numbytes
+@vrindex GNU.sparse.numbytes, extended header variable
 Size of the data block
 @end table
 
@@ -134,10 +142,13 @@ the @command{tar} implementation in question does not support POSIX
 format, it will also extract a file containing extension header
 attributes.  This file can be used to expand the file to its original
 state.  However, posix-aware @command{tar}s will usually ignore the
-unknown variables, which makes restoring the file much more
-difficult@FIXME-xref{how to extract sparse file using third-party @command{tar}s}.
+unknown variables, which makes restoring the file more
+difficult.  @xref{extracting sparse v.0.x, Extraction of sparse
+members in v.0.0 format}, for the detailed description of how to
+restore such members using non-GNU @command{tar}s.
 @end enumerate
 
+@cindex sparse formats, v.0.1
 @GNUTAR{} 1.15.2 introduced sparse format version @code{0.1}, which
 attempted to solve these problems.  As its predecessor, this format
 stores sparse map in the extended POSIX header.  It retains
@@ -147,6 +158,7 @@ it uses a single variable:
 
 @table @code
 @item GNU.sparse.map
+@vrindex GNU.sparse.map, extended header variable
 Map of non-null data chunks.  It is a string consisting of
 comma-separated values "@var{offset},@var{size}[,@var{offset-1},@var{size-1}...]" 
 @end table
@@ -158,6 +170,7 @@ is replaced with a special name, constructed using the following pattern:
 %d/GNUSparseFile.%p/%f
 @end smallexample
 
+@vrindex GNU.sparse.name, extended header variable
 The real name of the sparse file is stored in the variable
 @code{GNU.sparse.name}.  Thus, those @command{tar} implementations
 that are not aware of GNU extensions will at least extract the files
@@ -171,8 +184,8 @@ header variable, this possibly can confuse some tars.
 
 @node PAX 1
 @appendixsubsec PAX Format, Version 1.0
-@UNREVISED{}
 
+@cindex sparse formats, v.1.0
 The version @code{1.0} of sparse format was introduced with @GNUTAR{}
 1.15.92.  Its main objective was to make the resulting file
 extractable with little effort even by non-posix aware @command{tar}
@@ -182,9 +195,11 @@ identify the format being used:
 
 @table @code
 @item GNU.sparse.major
+@vrindex GNU.sparse.major, extended header variable
 Major version
 
 @item GNU.sparse.minor
+@vrindex GNU.sparse.minor, extended header variable
 Minor version
 @end table
 
@@ -195,6 +210,8 @@ constructed using the following pattern:
 %d/GNUSparseFile.%p/%f
 @end smallexample
 
+@vrindex GNU.sparse.name, extended header variable, in v.1.0
+@vrindex GNU.sparse.realsize, extended header variable
 The real name of the sparse file is stored in the variable
 @code{GNU.sparse.name}.  The real size of the file is stored in the
 variable @code{GNU.sparse.realsize}.
@@ -211,7 +228,7 @@ The format is designed in such a way that non-posix aware tars and tars not
 supporting @code{GNU.sparse.*} keywords will extract each sparse file
 in its condensed form with the file map prepended and will place it
 into a separate directory.  Then, using a simple program it would be
-possible to expand the file to its original form even without GNU tar.
-@FIXME-xref{how to extract sparse file using third-party
-@command{tar}s}. @FIXME{Write the program and give its URL here}.
+possible to expand the file to its original form even without @GNUTAR{}.
+@xref{Sparse Recovery}, for the detailed information on how to extract
+sparse members without @GNUTAR{}.
  

doc/tar.texi

@@ -13,9 +13,9 @@
 @c Maintenance notes:
 @c  1. Pay attention to @FIXME{}s and @UNREVISED{}s
 @c  2. Before creating final variant:
-@c    1.1. Run `make check-options' to make sure all options are properly
+@c    2.1. Run `make check-options' to make sure all options are properly
 @c         documented;
-@c    2.1. Run `make master-menu' (see comment before the master menu).
+@c    2.2. Run `make master-menu' (see comment before the master menu).
 
 @include rendition.texi
 @include value.texi
@@ -526,7 +526,7 @@ pipes).  @command{tar} may even access remote devices or files (as archives).
 You can use @command{tar} archives in many ways.  We want to stress a few
 of them: storage, backup, and transportation.
 
-@FIXME{the following table entries need a bit of work..}
+@FIXME{the following table entries need a bit of work.}
 @table @asis
 @item Storage
 Often, @command{tar} archives are used to store related files for
@@ -8573,6 +8573,7 @@ describe the required procedures in detail.
 @node Split Recovery
 @subsubsection Extracting Members Split Between Volumes
 
+@cindex Mutli-volume archives, extracting using non-GNU tars
 If a member is split between several volumes of an old GNU format archive
 most third party @command{tar} implementation will fail to extract
 it.  To extract it, use @command{tarcat} program (@pxref{Tarcat}).
@@ -8587,6 +8588,7 @@ extract them using a third-party @command{tar}:
 $ @kbd{tarcat vol-1.tar vol-2.tar vol-3.tar | tar xf -}
 @end smallexample
 
+@cindex Mutli-volume archives in PAX format, extracting using non-GNU tars
 You could use this approach for many (although not all) PAX
 format archives as well.  However, extracting split members from a PAX
 archive is a much easier task, because PAX volumes are constructed in
@@ -8678,6 +8680,7 @@ members.  Read further to learn more about them.
 @node Sparse Recovery
 @subsubsection Extracting Sparse Members
 
+@cindex sparse files, extracting with non-GNU tars
 Any @command{tar} implementation will be able to extract sparse members from a
 PAX archive.  However, the extracted files will be @dfn{condensed},
 i.e. any zero blocks will be removed from them.  When we restore such
@@ -8685,11 +8688,13 @@ a condensed file to its original form, by adding zero bloks (or
 @dfn{holes}) back to their original locations, we call this process
 @dfn{expanding} a compressed sparse file.
 
+@pindex xsparse
 To expand a file, you will need a simple auxiliary program called
 @command{xsparse}.  It is available in source form from
 @uref{http://www.gnu.org/@/software/@/tar/@/utils/@/xsparse.html, @GNUTAR{}
 home page}.
 
+@cindex sparse files v.1.0, extracting with non-GNU tars
 Let's begin with archive members in @dfn{sparse format
 version 1.0}@footnote{@xref{PAX 1}.}, which are the easiest to expand.
 The condensed file will contain both file map and file data, so no
@@ -8792,6 +8797,9 @@ Done
 @end group
 @end smallexample
 
+@anchor{extracting sparse v.0.x}
+@cindex sparse files v.0.1, extracting with non-GNU tars
+@cindex sparse files v.0.0, extracting with non-GNU tars
 An @dfn{extended header} is a special @command{tar} archive header
 that precedes an archive member and contains a set of
 @dfn{variables}, describing the member properties that cannot be
@@ -10165,22 +10173,10 @@ added later.  To label subsequent volumes, specify
 @option{--label=@var{archive-label}} again in conjunction with the
 @option{--append}, @option{--update} or @option{--concatenate} operation.
 
-@FIXME{This is no longer true: Multivolume archives in @samp{POSIX}
-format can be extracted using any posix-compliant tar
-implementation.  The split members can then be recreated from parts
-using a simple shell script. Provide more information about it:}
-Beware that there is @emph{no} real standard about the proper way, for
-a @command{tar} archive, to span volume boundaries.  If you have a
-multi-volume created by some vendor's @command{tar}, there is almost
-no chance you could read all the volumes with @GNUTAR{}.
-The converse is also true: you may not expect
-multi-volume archives created by @GNUTAR{} to be
-fully recovered by vendor's @command{tar}.  Since there is little
-chance that, in mixed system configurations, some vendor's
-@command{tar} will work on another vendor's machine, and there is a
-great chance that @GNUTAR{} will work on most of
-them, your best bet is to install @GNUTAR{} on all
-machines between which you know exchange of files is possible.
+Notice that multi-volume support is a GNU extension and the archives
+created in this mode should be read only using @GNUTAR{}.  If you
+absolutely have to process such archives using a third-party @command{tar}
+implementation, read @ref{Split Recovery}.
 
 @node Tape Files
 @subsection Tape Files