Gitignore

gitignore is a plain text file used by Git to determine which files and directories should be ignored by version control. It helps keep a repository clean by excluding build outputs, locally generated data, and other environment-specific files from being committed. A repository can contain a .gitignore at the root and additional .gitignore files in subdirectories to apply rules locally. A global ignore list can also be configured so certain patterns apply across all repositories on a system.

Pattern syntax is defined per line in a .gitignore file. Lines starting with # are comments, and blank lines are ignored. Each non-comment line is a pattern or file name. Patterns are matched relative to the directory containing the .gitignore file. A leading slash anchors the pattern to the repository root for that file. A trailing slash matches directories only. Wildcards include * (any sequence of characters), ? (a single character), and character ranges in brackets []. A double star ** matches across directory boundaries. A pattern beginning with ! negates a previous ignore rule, re-including matching files.

Common examples:

- *.log

- build/

- node_modules/

- /config/secrets.yml

- /vendor/

- !config/keep.config

Notes on behavior: If a file is already tracked by Git, adding it to .gitignore will not untrack it. To stop tracking it while leaving the file in the working directory, use git rm --cached <path>. Additional ignore locations include the .git/info/exclude file for per-repository exclusions and a global excludes file via core.excludesFile, which is useful for system-wide patterns like OS-specific files.

---