[PATCH] doc: Explain when guix edit is read-only.

[myglc2 <myglc2@gmail.com>]

* doc/guix.texi (Invoking guix edit): Explain when you can and can't
  edit the recipe
---
 doc/guix.texi | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/doc/guix.texi b/doc/guix.texi
index e7b233d..914d24d 100644
--- a/doc/guix.texi
+++ b/doc/guix.texi
@@ -4485,7 +4485,7 @@ You can freely access a huge library of build logs!
 
 @cindex package definition, editing
 So many packages, so many source files!  The @command{guix edit} command
-facilitates the life of packagers by pointing their editor at the source
+facilitates the life of users and packagers by pointing their editor at the source
 file containing the definition of the specified packages.  For instance:
 
 @example
@@ -4494,9 +4494,15 @@ guix edit gcc@@4.9 vim
 
 @noindent
 launches the program specified in the @code{VISUAL} or in the
-@code{EDITOR} environment variable to edit the recipe of GCC@tie{}4.9.3
+@code{EDITOR} environment variable to view the recipe of GCC@tie{}4.9.3
 and that of Vim.
 
+If you are using a Guix Git checkout (@pxref{Building from Git}), or
+have created your own packages on ‘GUIX_PACKAGE_PATH’ (*note Defining
+Packages::), you will be able to edit the package recipes. Otherwise,
+you will be able to examine the read-only recipes for packages currently
+in the store.
+
 If you are using Emacs, note that the Emacs user interface provides the
 @kbd{M-x guix-edit} command and a similar functionality in the ``package
 info'' and ``package list'' buffers created by the @kbd{M-x
-- 
2.9.1