Pull is not possible because you have unmerged files.

之前项目大多使用svn，对于git的使用很少，最近项目都使用了git在操作过程中，遇到一些问题在这儿记录下。

在git pull的过程中，如果有冲突，那么除了冲突的文件之外，其它的文件都会做为staged区的文件保存起来。
重现：
$ git pull
A    Applications/Commerce/BookingAnalysis.java

A    Applications/Commerce/ClickSummaryFormatter.java

M    Applications/CommerceForecasting/forecast/Forecast.java

A    Applications/CommerceForecasting/forecast/ForecastCurveProviderCategory.java

M    Applications/CommerceForecasting/forecast/ForecastProvider.java

M    Applications/CommerceForecasting/forecast/InputPropertyItem.java

......
A    Applications/LocalezeImporter/com/tripadvisor/feeds/SingleMenuLocalezeMatcher.java

A    Applications/LocalezeImporter/com/tripadvisor/feeds/TypeCategory.java
Pull is not possible because you have unmerged files.
Please, fix them up in the work tree, and then use 'git add/rm <file>'
as appropriate to mark resolution, or use 'git commit -a'.

通过git status你会发现下面古怪的事情：

zhonghua@pts/ttys000 $ git status

# On branch sns

# Your branch and 'snsconnect/sns' have diverged,

# and have 1 and 52 different commit(s) each, respectively.

#

# Changes to be committed:

#

#    new file:   src/config/features_daodao.ini

#    new file:   src/config/services.xml

#    new file:   src/config/svnroot/hooks/mailer.conf

#    new file:   src/config/svnroot/hooks/mailer.py

#    new file:   src/config/svnroot/hooks/post-commit

#    new file:   src/config/svnroot/hooks/pre-commit

#    new file:   src/config/svnroot/hooks/prerelease_notifications.py

#    new file:   src/config/svnroot/hooks/run_checks.py

…….

# Untracked files:

#   (use "git add <file>..." to include in what will be committed)

#

#    _build/

#    css/combined/

#    css/gen/

#    daodao-site.patch

#    daodao-site.patch1

#    js/combined/

#    js/gen/

#    lib/weibo/

#    src/bin/

Pull is not possible because you have unmerged files.
解决：
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。