1. Pull is not possible because you have unmerged files.
症状：pull的时候
$ git pull
Pull is not possible because you have unmerged files.
Please, fix them up in the work tree, and then use 'git add/rm '
as appropriate to mark resolution, or use 'git commit -a'
应该是因为local文件冲突了
解决方法：
引用——
“
1.pull会使用git merge导致冲突，需要将冲突的文件resolve掉 git add -u, git commit之后才能成功pull.
2.如果想放弃本地的文件修改，可以使用git reset --hard FETCH_HEAD，FETCH_HEAD表示上一次成功git pull之后形成的commit点。然后git pull.
注意：
git merge会形成MERGE-HEAD(FETCH-HEAD) 。git push会形成HEAD这样的引用。HEAD代表本地最近成功push后形成的引用。
”
就我的经验，有时候会莫名其妙地出现这种状况，而且Untracked files 还特别多（实际上自己可能只改了一两个文件），所以只好先保存好自己确定做出的local的修改，然后用git reset --hard FETCH_HEAD回到上次成功pull之后的点，然后再pull就没有问题了
2.You are not currently on a branch.
症状：有一次pull的时候又出现冲突，这回用“git reset --hard FETCH_HEAD”方法都不行了，出现：
$ git pull
You are not currently on a branch, so I cannot use any
'branch.<branchname>.merge' in your configuration file.
Please specify which remote branch you want to use on the command
line and try again (e.g. 'git pull <repository><refspec>').
See git-pull(1) for details.
解决方法：
首先git checkout -b temp
其次git checkout master
即可恢复到master repository的状态，然后就可以pull了
参考：
http://skywhsq1987.iteye.com/blog/1814137
http://slacy.com/blog/2011/04/git-pull-says-you-are-not-currently-on-a-branch/
http://ddmytrenko.blogspot.com/2012/03/git-not-currently-on-any-branch.html
