Version Control with Git

The .gitignore File

Earlier in this chapter, you saw how to use the .gitignore file to pass over main.o, an irrelevant file. As in that example, you can skip any file by adding its name to .gitignore in the same directory. Additionally, you can ignore the file everywhere by adding it to the .gitignore file in the top-most directory of your repository.

But Git also supports a much richer mechanism. A .gitignore file can contain a list of filename patterns that specify what files to ignore. The format of .gitignore is as follows:

• Blank lines are ignored, and lines starting with a hash mark (#) can be used for comments. However, the hash mark does not represent a comment if it follows other text on the line.

• A simple, literal filename matches a file in any directory with that name.

• A directory name is marked by a trailing slash character (/). This matches the named directory and any subdirectory but does not match a file or a symbolic link.

• A pattern containing shell globbing characters, such as an asterisk (*), is expanded as a shell glob pattern. Just as in standard shell globbing, the match cannot extend across directories and so an asterisk can match only a single file or directory name. But an asterisk can still be part of a pattern that includes slashes to specify directory names as part of the pattern (e.g., debug/32bit/*.o).

• An initial exclamation point (!) inverts the sense of the pattern on the rest of the line. Additionally, any file excluded by an earlier pattern but matching ...