documentation: update documentation for SRCREV variable

* Add note about specifying a full revision ID to prevent querying the
  remote server on every parse
* Mercurial also supports this variable

(From yocto-docs rev: 47ce273dd751b0ae32b5c53310b6aedc4dade2ef)

Signed-off-by: Paul Eggleton <paul.eggleton@linux.intel.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

1 files changed, 5 insertions, 1 deletions

diff --git a/documentation/poky-ref-manual/ref-variables.xml b/documentation/poky-ref-manual/ref-variables.xml
index b87ee42fe9..f942cc7319 100644
--- a/documentation/poky-ref-manual/ref-variables.xml
+++ b/documentation/poky-ref-manual/ref-variables.xml
@@ -969,7 +969,11 @@
             <glossdef>
                 <para>
                     The revision of the source code used to build the package.
-                    This variable applies to Subversion, GitT, or Bazaar only.
+                    This variable applies to Subversion, Git, Mercurial and Bazaar
+                    only. Note that if you wish to build a fixed revision and you wish
+                    to avoid performing a query on the remote repository every time
+                    BitBake parses your recipe, you should specify a SRCREV that is a
+                    full revision identifier (and not just a tag).
                 </para>
             </glossdef>
         </glossentry>