1.git pull报错：
There is no tracking information for the current branch.
Please specify which branch you want to merge with.
See git-pull(1) for details.
git pull <remote> <branch>
If you wish to set tracking information for this branch you can do so with:
git branch --set-upstream-to=origin/<branch> master
原因：本地仓库和远程仓库的分支没有做关联。
解决：运行git branch --set-upstream-to=origin/<branch> master，给本地master分支设置一个上游分支或者说是跟踪分支。
2.git pull报错:
fatal: refusing to merge unrelated histories
原因：本地仓库和远程仓库存在不同的提交记录。
解决：运行git pull origin master --allow-unrelated-histories，后面加上--allow-unrelated-histories，把两个不相干的分支进行强行合并
3.git pull报错:
fatal: unable to access 'https://github.com/xxxx/xxxx.git/': SSL certificate problem: unable to get local issuer certificate
原因：一般是连接github的时候会报的错，一般是这是因为服务器的SSL证书没有经过第三方机构的签署，所以才报错。
解决：参考网上解决办法，输入下面代码，解除ssl验证后，再次git即可。
git config --global http.sslVerify false
4.git push报错：
fatal: The current branch wangxiao has no upstream branch.
To push the current branch and set the remote as upstream
原因：这是因为本地的分支没有和远程分支建立联系
解决：执行 git push --set-upstream origin master，或者在pull的时候就执行git branch --set-upstream-to=origin/<branch> master建立上游分支。
5.git push报错：
fatal: The upstream branch of your current branch does not match
the name of your current branch. To push to the upstream branch
on the remote, use
git push origin HEAD:main
To push to the branch of the same name on the remote, use
git push origin HEAD
To choose either option permanently, see push.default in 'git help config'.
原因：本地仓库和远程仓库的分支名不同，不知道要push那个本地分支到远程分支。我这边github新仓库的默认分支是main，本地仓库分支是master。
解决：共3中方法：
1.更改远程仓库分支名，把远程分支改成master。
2.①更改本地仓库分支名为main：
git branch -m main
②然后执行下面代码，忽略本地和远程仓库不同的提交记录，强行合并。
git pull origin main --allow-unrelated-histories
③执行下面代码，把本地分支和远程分支关联。
git branch --set-upstream-to=origin/main main
注意：如果先进行步骤③，再进行步骤②的话，在执行步骤③的时候就会报错：
error: the requested upstream branch 'origin/main' does not exist
hint:
hint: If you are planning on basing your work on an upstream
hint: branch that already exists at the remote, you may need to
hint: run "git fetch" to retrieve it.
hint:
hint: If you are planning to push out a new local branch that
hint: will track its remote counterpart, you may want to use
hint: "git push -u" to set the upstream config as you push.
3.采用git的push默认配置push.default中的upstream选项，从哪pull的就push到哪。
git config push.default upstream
6.git branch --set-upstream-to=origin/master master报错:
error: the requested upstream branch 'origin/master' does not exist
hint:
hint: If you are planning on basing your work on an upstream
hint: branch that already exists at the remote, you may need to
hint: run "git fetch" to retrieve it.
hint:
hint: If you are planning to push out a new local branch that
hint: will track its remote counterpart, you may want to use
hint: "git push -u" to set the upstream config as you push.
原因：我这边报错的原因是因为远程仓库是github，现在的github把默认分支改成了main，而本地git的默认分支是master。
解决：把origin/master改成origin/main就行了：
git branch --set-upstream-to=origin/main master
7.git pull origin master --allow-unrelated-histories报错：
fatal: couldn't find remote ref master
原因：还是因为现在的github建立的仓库默认分支是main，没有和本地仓库关联。
解决：运行下面代码：
git pull origin main --allow-unrelated-histories
