[PATCH] doc: Explain --localstatedir some more.

[Jookia]

This should hopefully stop people from running in to issues when
building Guix from source as they have in the past.

* doc/guix.texi (Requirements): Add explanation of the localstatedir flag.
  Discuss how to keep compatibility with binary installation and the package.
---
 doc/guix.texi | 17 +++++++++++++++--
 1 file changed, 15 insertions(+), 2 deletions(-)

diff --git a/doc/guix.texi b/doc/guix.texi
index 0e8e5ad..94323ff 100644
--- a/doc/guix.texi
+++ b/doc/guix.texi
@@ -16,8 +16,9 @@ Copyright @copyright{} 2013 Nikita address@hidden
 Copyright @copyright{} 2015, 2016 Mathieu address@hidden
 Copyright @copyright{} 2014 Pierre-Antoine address@hidden
 Copyright @copyright{} 2015 Taylan Ulrich Bayırlı/address@hidden
-Copyright @copyright{} 2015, 2016 Leo Famulari
-Copyright @copyright{} 2016 Ben Woodcroft
+Copyright @copyright{} 2015, 2016 Leo address@hidden
+Copyright @copyright{} 2016 Ben address@hidden
+Copyright @copyright{} 2016 Jookia
 
 Permission is granted to copy, distribute and/or modify this document
 under the terms of the GNU Free Documentation License, Version 1.3 or
@@ -514,6 +515,18 @@ manager} is available, you
 can instead configure Guix with @code{--disable-daemon}.  In that case,
 Nix replaces the three dependencies above.
 
+Tradionally Guix stores its state in @var{localstatedir} as most GNU
+applications do.  In certain situations you may want to change this setting,
+by passing the @address@hidden flag to @command{configure}.
+
+The binary installation of Guix and the package of Guix both use @code{/var} as
+their @var{localstatedir} path.  If you wish to have compatibility with one of
+these versions of Guix installed or you plan to install, passing
address@hidden/var} to @command{configure} will allow your compiled Guix
+to share state.  Be warned that sharing the same Guix store (usually located at
address@hidden/gnu}) with different sets of state could cause issues such as 
garbage
+collecting store entries that are alive in one Guix's state but not the 
other's.
+
 Guix is compatible with Nix, so it is possible to share the same store
 between both.  To do so, you must pass @command{configure} not only the
 same @code{--with-store-dir} value, but also the same
-- 
2.7.0