Ensure `git-pull` fails if `git-merge` fails.

If git-merge exits with a non-zero exit status so should git-pull.
This way the caller of git-pull knows the task did not complete
successfully simply by checking the process exit status.
Signed-off-by: NShawn O. Pearce <spearce@spearce.org>
Signed-off-by: NJunio C Hamano <junkio@cox.net>

git-pull.sh

@@ -119,5 +119,5 @@ case "$strategy_args" in
 esac
 
 merge_name=$(git-fmt-merge-msg <"$GIT_DIR/FETCH_HEAD") || exit
-git-merge $no_summary $no_commit $squash $strategy_args \
+exec git-merge $no_summary $no_commit $squash $strategy_args \
 	"$merge_name" HEAD $merge_head