Fix latest_release hash test

Obtain the version and latest_release tag commit hashes before changing
into the cloned repository so that all tagging and pushing happens on
the outer repository.

bin/release

@@ -36,7 +36,9 @@ setup() {
     esac
 
     LATEST_TAG_SHA=$(git rev-parse $LATEST_TAG)
+    LATEST_TAG_COMMIT_SHA=$(git rev-list -1 $LATEST_TAG)
     LATEST_RELEASE_SHA=$(git rev-parse latest_release)
+    LATEST_RELEASE_COMMIT_SHA=$(git rev-list -1 latest_release)
     VERSION=${LATEST_TAG}
     # NB does not check that this tag is on master
     RELEASE_DIR=./releases/$LATEST_TAG
@@ -185,8 +187,10 @@ publish() {
     else
         echo "** Release draft detected"
         echo "== Sanity checks"
-        if ! [ $(git rev-list -1 $LATEST_TAG) == $(git rev-list -1 latest_release) ]; then
-            echo -e "\u2757 The tag latest_release does not point to the same commit as $LATEST_TAG"
+        if ! [ "$LATEST_TAG_COMMIT_SHA" == "$LATEST_RELEASE_COMMIT_SHA" ] ; then
+            echo -e "\u2757 The tag latest_release does not point to the same commit as $LATEST_TAG" >&2
+            echo "You may need to" >&2
+            echo -e "\tgit tag -af latest_release $LATEST_TAG" >&2
             exit 1
         fi
 
@@ -195,8 +199,7 @@ publish() {
             echo -e "\u2757 Tag latest_release is not on GitHub, or is not the same as the local tag" >&2
             echo -e "\thttps://github.com/$GITHUB_USER/weave/tags" >&2
             echo "You may need to" >&2
-            echo -e "\tgit tag -af latest_release"
-            echo -e "\tgit push -f git@github.com:$GITHUB_USER/weave latest_release"
+            echo -e "\tgit push -f git@github.com:$GITHUB_USER/weave latest_release" >&2
             exit 1
         fi
         echo '** Sanity checks OK for publishing tag' $LATEST_TAG as $DOCKERHUB_USER/weave:$VERSION