doc: Explain when guix edit is read-only.

* doc/guix.texi (Invoking guix edit): Explain when you can and can't
  edit the recipe.

Signed-off-by: Alex Kost <alezost@gmail.com>

1 files changed, 10 insertions, 3 deletions

diff --git a/doc/guix.texi b/doc/guix.texi
index 9703c72ff5..ec22d94a9a 100644
--- a/doc/guix.texi
+++ b/doc/guix.texi
@@ -4536,8 +4536,9 @@ 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
-file containing the definition of the specified packages.  For instance:
+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
 guix edit gcc@@4.9 vim
@@ -4545,9 +4546,15 @@ 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 @code{GUIX_PACKAGE_PATH}
+(@pxref{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