@command{etc/indent-code.el} script to do that automatically for you
(@pxref{Formatting Code}).
+@item
+When possible, use mirrors in the source URL (@pxref{Invoking guix download}).
+Use reliable URLs, not generated ones. For instance, GitHub archives are not
+necessarily identical from one generation to the next, so in this case it's
+often better to clone the repository. Don't use the @command{name} field in
+the URL: it is not very useful and if the name changes, the URL will probably
+be wrong.
+
@end enumerate
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