[gnome-continuous-yocto/gnomeostree-3.28-rocko: 1677/8267] bitbake: bitbake-user-manual: Added non-existant variable expansion

[Emmanuele Bassi <ebassi src gnome org>]

commit f0e73a4b65b8632bf9c9642faf8e1b22a628d88e
Author: Scott Rifenbark <srifenbark gmail com>
Date:   Fri Jul 22 08:36:09 2016 -0700

    bitbake: bitbake-user-manual: Added non-existant variable expansion
    
    Fixes [YOCTO #10003]
    
    I added a small paragraph explaining what happens when expansion
    of a variable that does not exist occurs.
    
    (Bitbake rev: 8006da3f229d0227215ccd59cd273edacf72f9ce)
    
    Signed-off-by: Scott Rifenbark <srifenbark gmail com>
    Signed-off-by: Richard Purdie <richard purdie linuxfoundation org>

 .../bitbake-user-manual-metadata.xml               |   11 +++++++++++
 1 files changed, 11 insertions(+), 0 deletions(-)
---
diff --git a/bitbake/doc/bitbake-user-manual/bitbake-user-manual-metadata.xml 
b/bitbake/doc/bitbake-user-manual/bitbake-user-manual-metadata.xml
index fe04103..ce0e84d 100644
--- a/bitbake/doc/bitbake-user-manual/bitbake-user-manual-metadata.xml
+++ b/bitbake/doc/bitbake-user-manual/bitbake-user-manual-metadata.xml
@@ -86,6 +86,17 @@
                 <link linkend='immediate-variable-expansion'>immediate variable expansion</link>
                 operator (i.e. ":=").
             </para>
+
+            <para>
+                If the variable expansion syntax is used on a variable that
+                does not exist, the string is kept as is.
+                For example, given the following assignment,
+                <filename>BAR</filename> expands to the literal string
+                "${FOO}" as long as <filename>FOO</filename> does not exist.
+                <literallayout class='monospaced'>
+     BAR = "${FOO}"
+                </literallayout>
+            </para>
         </section>
 
         <section id='setting-a-default-value'>