What is .gitignore?
If we add up .gitignore file into our repository, Git actually determines what files or pattern of the files that should not be included in the repository.
Suppose, if we want to add a java project, running a maven build for the project creates a /target folder wherein all the created JARs will be stored.
We don’t want to clutter our repository space with un-necessary JAR files.
Hence we tend to ignore the entire folder by adding the pattern to .gitignore.
Same applies for the project file for other projects.
Though there is a list of well know .gitignore files available of every kind of project that we generally work on, ranging from java to python etc.
Below is the .gitignore file created for maven project.
Though we have flexibility to choose a predefined .gitingore file,
You still can create a custom .gitignore file.
1.) Ignoring a specific file
You may tend to ignore a specific file by providing its relative complete path with extension.
Suppose, if we don’t want a CSV file called as “dummy.csv” which exists in output folder.
We can write the path in the output folder as
/output/dummy.csv
2.) Ignoring a folder and its content
If we want to ignore a folder and its content, provide the folder name followed by *
Suppose, if we don’t want to add any file present inside the output folder of the repository.
We can simply write it by
/output/*
3.) Ignoring a file extension
Suppose, if we want to ignore certain type of file to be present in the repository, we can do so by specifying the extension of the file.
E.g
*.com, *.zip, *.JAR etc.
Conclusion
The above tutorial helps you Understand, how can you create a pre-existing .gitignore file or how you can manually create your own version of .gitignore to avoid adding a file to file pattern into the repository.
References
https://www.atlassian.com/git/tutorials/saving-changes/gitignore
https://coursework.vschool.io/create-a-gitignore/