git - 如何取消忽略

Question

如题，之前本人在sourcetree不小心忽略了某个项目的文件，这两天想要上传到自己的github才发现好像被我忽略了，但是本人使用git还不是很熟练，请问各位大牛使用sourcetree要如何取消忽略或者如何使用linux命令行取消忽略。
在搜索的过程中发现gitignore，但是不知道怎么使用！
先在此谢谢各位！
补充一下，刚刚根据@manong 还有@Bpazy 的回答和评论，我查看了一下我的文件，我感觉可能是我对git不了解而提出的问题导致误导了他们，贴上图片方便各位。

我发现并没有那个文件夹，可能是我的描述有错误。然后呢，我又试了一下，刚刚压缩了我的项目文件夹，发现git居然能够追踪到，而且sourcetree提示了大于10m，是否跟踪。

会不会是git的文件大小的限制之类的呢？

Answer 1

Look for a file called .gitignore in your code directory. After opening, it will contain all the files to be ignored. Paths and wildcards are supported

Answer 2

Because I don’t know where the ignore file exists under SourceTree, so I can only tell you how to submit the ignore file under SourceTree.

Then find the file you want to submit in Unstaged files. After selecting File status, the number of files you want to submit will appear, but at this time you still cannot see the file and cannot submit it

In this way, you can see the ignored files and commit will also be lit.

Supplement:
I tested it, I was stupid and couldn’t find the .gitignore file, but the ignored file will not disappear and is still in the project directory, so just submit it directly (ノ_＜)

Answer 3

Git - gitignore Documention