Subject: [PATCH 2/2] doc: Mention how to remedy "source file ... newer than compiled error".

From: jgart <[email-masked]>
Date: Wed, 15 Dec 2021 06:20:42 -0500

From: Guix Together <[email-masked]>

* doc/contributing.texi (Running Guix Before It Is Installed): Mention
how to remedy "source file ... newer than compiled" error by running
`make -j`.

Co-authored-by: jgart <[email-masked]>
Co-authored-by: Julien Lepiller <[email-masked]>
Co-authored-by: Ryan Prior <[email-masked]>
Co-authored-by: Blake Shaw <[email-masked]>
---
 doc/contributing.texi | 18 ++++++++++++++++++
 1 file changed, 18 insertions(+)

diff --git a/doc/contributing.texi b/doc/contributing.texi
index 1bcb550aac..fa8dd376d2 100644
--- a/doc/contributing.texi
+++ b/doc/contributing.texi
@@ -243,6 +243,24 @@ local source tree; it simply updates the @file{~/.config/guix/current}
 symlink (@pxref{Invoking guix pull}).  Run @command{git pull} instead if
 you want to upgrade your local source tree.
 
+Sometimes, especially if you have recently updated your repository,
+running @command{./pre-inst-env} will print a message similar to the
+following example:
+
+@example
+;;; note: source file /home/user/projects/guix/guix/progress.scm
+;;;       newer than compiled /home/user/projects/guix/guix/progress.go
+@end example
+
+This is only a note and you can safely ignore it. You can get rid of
+the message by running @command{make -j}. Until you do, Guile will run
+slightly slower because it will interpret the code instead of using
+prepared Guile object (@code{.go}) files.
+
+You can run @command{make} automatically as you work using
+@command{watchexec} from the @code{watchexec} package. For example,
+to build again each time you update a package file, you can run
+@command{watchexec -w gnu/packages make -j}.
 
 @node The Perfect Setup
 @section The Perfect Setup
-- 
2.34.0