doc: explain why single-quoting is better

* doc/autoconf.texi (Build Directories): Explain single-quoting.
Reported by Markus Elfring in
<http://savannah.gnu.org/support/?108262>.

diff --git a/doc/autoconf.texi b/doc/autoconf.texi
index bf4823d57f5ab80aac67590ab0c287c2c42be21e..c54c5b351a2a33f61928fdba78208d6cdbbcff40 100644 (file)
--- a/doc/autoconf.texi
+++ b/doc/autoconf.texi
@@ -3148,7 +3148,10 @@ versions of @command{make} do not set @code{$<} in explicit rules; they
 expand it to an empty value.
 
 Instead, Make command lines should always refer to source
-files by prefixing them with @samp{$(srcdir)/}.  For example:
+files by prefixing them with @samp{$(srcdir)/}.  It's safer
+to quote the source directory name, in case it contains characters that
+are special to the shell.  Because @samp{$(srcdir)} is expanded by Make,
+single-quoting works and is safer than double-quoting.  For example:
 
 @example
 time.info: time.texinfo