bitbake: ast/ConfHandler: Add a syntax to clear variable

unset VAR
will clear variable VAR
unset VAR[flag]
will clear flag "flag" from var VAR

(Bitbake rev: bedbd46ece8d1285b5cd2ea07dc64b4875b479aa)

Signed-off-by: Jérémy Rosen <jeremy.rosen@openwide.fr>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

1 files changed, 17 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 5df00050ce..64f08157f6 100644
--- a/bitbake/doc/bitbake-user-manual/bitbake-user-manual-metadata.xml
+++ b/bitbake/doc/bitbake-user-manual/bitbake-user-manual-metadata.xml
@@ -435,6 +435,23 @@
             </para>
         </section>
 
+        <section id='unsetting-variables'>
+            <title>Unseting variables</title>
+
+            <para>
+                It is possible to completely remove a variable or a variable flag 
+                from BitBake's internal data dictionary by using the "unset" keyword.
+                Here is an example:
+                <literallayout class='monospaced'>
+        unset DATE
+        unset do_fetch[noexec]
+                </literallayout>
+                These two statements remove the <filename>DATE</filename> and the 
+                <filename>do_fetch[noexec]</filename> flag.
+            </para>
+
+        </section>
+
         <section id='providing-pathnames'>
             <title>Providing Pathnames</title>