03/12: doc: Clarify substitute* docstring with an example.

[guix-commits]

civodul pushed a commit to branch master
in repository guix.

commit 199218e372f490ae8158bac99d3a434557ef1bec
Author: Gabriel Wicki <gabriel@erlikon.ch>
AuthorDate: Thu Apr 13 10:31:57 2023 +0200

    doc: Clarify substitute* docstring with an example.
    
    * doc/guix.texi (Build Utilities): Update the corresponding passage.
    
    Co-authored-by: Ludovic Courtès <ludo@gnu.org>
---
 doc/guix.texi | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/doc/guix.texi b/doc/guix.texi
index 2871fb9957..31ebcf9db4 100644
--- a/doc/guix.texi
+++ b/doc/guix.texi
@@ -10379,7 +10379,9 @@ Alternatively, @var{file} may be a list of file names, 
in which case
 they are all subject to the substitutions.
 
 Be careful about using @code{$} to match the end of a line; by itself it
-won't match the terminating newline of a line.
+won't match the terminating newline of a line.  For example, to match a
+whole line ending with a backslash, one needs a regex like
+@code{"(.*)\\\\\n$"}.
 @end defmac
 
 @subsection File Search