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。