scripts: aosp-merger: Use existing BRANCH variable

Change-Id: I589aa4570dd6b4f340eb90eeae13f065b0b3b9a3
diff --git a/aosp-merger/aosp-merger.sh b/aosp-merger/aosp-merger.sh
index 6bb49e3..8433497 100755
--- a/aosp-merger/aosp-merger.sh
+++ b/aosp-merger/aosp-merger.sh
@@ -99,7 +99,7 @@
 
     if [[ "${PROJECTOPERATION}" == "merge" ]]; then
         echo "#### Merging ${NEWTAG} into ${PROJECTPATH} ####"
-        git merge --log "${NEWTAG}" --into-name "$(repo info . | grep 'Manifest revision' | cut -f3 -d '/')"
+        git merge --log "${NEWTAG}" --into-name "${BRANCH}"
     elif [[ "${PROJECTOPERATION}" == "rebase" ]]; then
         echo "#### Rebasing ${PROJECTPATH} onto ${NEWTAG} ####"
         git rebase --onto "${NEWTAG}" "${OLDTAG}"