git merge 结果是 git merge Already up-to-date. 该怎么解决？

Question

我从远程仓库去拉取更新，如果用git pull会得到正常的结果

$ git pull local gaoyx_work
From localhost:~/publicOpinion
 * branch            gaoyx_work -> FETCH_HEAD
Merge made by recursive.
 workDir/dbConnector.php |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

但是使用git fetch和git merge则不能成功

$ git fetch local gaoyx_work
From localhost:~/publicOpinion
 * branch            gaoyx_work -> FETCH_HEAD
$ git merge local/gaoyx_work
Already up-to-date.

对于git merge不是很懂，不知道是怎么回事，也不知道该怎么解决