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gitignore

The .gitignore file is a crucial component in any Git repository. It instructs Git to ignore specific files or directories that should not be tracked or maintained in the version control system. This is particularly useful for excluding files that contain sensitive information, user-specific configurations, temporary files created by the development environment, or dependencies that can be installed via a package manager.

Syntax and Structure​

A .gitignore file uses glob patterns to match file names. Here's how it works:

  • Blank lines are ignored, which can be used for spacing and organization.
  • Lines starting with # are treated as comments.
  • Standard glob patterns are used for matching files or paths. These include:
    • * matches zero or more characters.
    • ? matches exactly one character.
    • [...] matches any character inside the brackets.
    • **/ matches any directories recursively.

Common Patterns​

# Ignore all .log files
*.log

# Ignore a specific file
secret.txt

# Ignore all files in a specific directory
tmp/*

# Ignore all .txt files in a specific directory
docs/*.txt

# Ignore a directory and everything inside it
node_modules/

# Ignore all .pdf files in any directory
**/*.pdf

Best Practices​

  • Global vs. Local .gitignore: You can have a global .gitignore file for all your projects and a local one for a specific project. The local .gitignore file is placed in the root of your repository.
  • Commit .gitignore Early: It's a good practice to add and commit your .gitignore file as early as possible in your project to prevent accidental inclusion of unwanted files.
  • Sensitive Data: If sensitive data was committed before it was added to .gitignore, simply adding it to .gitignore won't remove it from the history. You must use tools like git filter-branch or BFG Repo-Cleaner to remove it completely.
  • Templates: Many projects share similar .gitignore needs. Websites like gitignore.io offer templates for various project types, making it easy to start with a comprehensive .gitignore file.

Example .gitignore for a Java Project​

# Compiled class files
*.class

# Build directories
target/
out/

# Package Files
*.jar
*.war
*.nar
*.ear
*.zip
*.tar.gz
*.rar

# Maven
pom.xml.tag
pom.xml.releaseBackup
pom.xml.versionsBackup
pom.xml.next
release.properties
dependency-reduced-pom.xml
buildNumber.properties
.mvn/timing.properties

# IntelliJ IDEA
.idea/
*.iml
*.iws

# Eclipse
.classpath
.project
.settings/

# Mac OS folder attributes
.DS_Store

In conclusion, a properly configured .gitignore file is essential for maintaining a clean and secure repository. It helps to minimize clutter and prevent the accidental commit of irrelevant or sensitive files.