kernel-yocto: replace --is-ancestor with basic git porcelain commands

--is-ancestor is a relatively new git option [commit 5907cda1, Aug 30 2012].
To support build machines with older versions of git installed, we can use
the basic porcelain commands to acheive the same check.

merge-base: "--is-ancestor A B" can be replaced with:

    if test "$(git rev-parse --verify A)" = "$(git merge-base A B)"

(From OE-Core rev: 2ddfffe52720d1df70b04131eac553776da7bc73)

Signed-off-by: Bruce Ashfield <bruce.ashfield@windriver.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

1 files changed, 1 insertions, 2 deletions

diff --git a/meta/classes/kernel-yocto.bbclass b/meta/classes/kernel-yocto.bbclass
index ee09769d46..929d64a290 100644
--- a/meta/classes/kernel-yocto.bbclass
+++ b/meta/classes/kernel-yocto.bbclass
@@ -131,8 +131,7 @@ do_patch() {
         # check to see if the specified SRCREV is reachable from the final branch.
         # if it wasn't something wrong has happened, and we should error.
         if [ "${machine_srcrev}" != "AUTOINC" ]; then
-                git merge-base --is-ancestor ${machine_srcrev} HEAD
-                if [ $? -ne 0 ]; then
+                if ! [ "$(git rev-parse --verify ${machine_srcrev})" = "$(git merge-base ${machine_srcrev} HEAD)" ]; then
                         bberror "SRCREV ${machine_srcrev} was specified, but is not reachable"
                         bbfatal "Check the BSP description for incorrect branch selection, or other errors."
                 fi