bug#61094: [PATCH] doc: Document 'shebang' for 'guix shell'.

[Ludovic Courtès]

Hi Simon,

Simon Tournier <zimon.toutoune@gmail.com> skribis:

> * doc/guix.texi (Invoking guix shell): Add a note mentioning how to use
> 'shebang'.

Applied with the changes below.  

Thanks!

Ludo’.

diff --git a/doc/guix.texi b/doc/guix.texi
index 9c1fc04265..aa98d7df4b 100644
--- a/doc/guix.texi
+++ b/doc/guix.texi
@@ -5940,16 +5940,19 @@ guix shell python python-numpy -- python3
 @end example
 
 @quotation Note
-@cindex shebang
-@command{guix shell} can be used as @emph{shebang}.  Consider the
-previous example as an executable Python script, the @emph{shebang}
-reads,
+@cindex shebang, for @command{guix shell}
+@command{guix shell} can be also be used as a script interpreter, also
+known as @dfn{shebang}.  Here is an example self-contained Python script
+making use of this feature:
 
 @example
-#!/usr/bin/env -S guix shell python python-nympy -- python3
+#!/usr/bin/env -S guix shell python python-numpy -- python3
+import numpy
+print("This is numpy", numpy.version.version)
 @end example
 
-All the @var{options} or convenience of @command{guix shell} apply.
+You may pass any @command{guix shell} option, but there's one caveat:
+the Linux kernel has a limit of 127 bytes on shebang length.
 @end quotation
 
 Development environments can be created as in the example below, which