git merge 結果是 git merge Already up-to-date. 怎麼解決？

Question

我從遠端倉庫去拉取更新，如果用git pull會得到正常的結果

$ 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則不能成功

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

對於git merge不是很懂，不知道是怎麼回事，也不知道該怎麼解決