在Pro Git一书中有如下描述

The rules for the patterns you can put in the .gitignore file are as follows:

• Blank lines or lines starting with # are ignored.

• Standard glob patterns work, and will be applied recursively throughout the entire working tree.

• You can start patterns with a forward slash (/) to avoid recursivity.

• You can end patterns with a forward slash (/) to specify a directory.

• You can negate a pattern by starting it with an exclamation point (!)

Glob patterns are like simplified regular expressions that shells use.

• An asterisk (*) matches zero or more characters;
• [abc] matches any character inside the brackets (in this case a, b, or c);
• a question mark (?) matches a single character;
• and brackets enclosing characters separated by a hyphen ([0-9]) matches any character between them (in this case 0 through 9).
• You can also use two asterisks to match nested directories; a/**/z would match a/z, a/b/z, a/b/c/z, and so on.

Here is another example .gitignore file:

# ignore all .a files
*.a
# but do track lib.a, even though you're ignoring .a files above
!lib.a
# only ignore the TODO file in the current directory, not subdir/TODO
/TODO
# ignore all files in any directory named build
build/
# ignore doc/notes.txt, but not doc/server/arch.txt
doc/*.txt
# ignore all .pdf files in the doc/ directory and any of its subdirectories
doc/**/*.pdf

翻译

• 空行或者以#开头的行是不生效的

• 标准的glob工作模式，遍历整个工作目录

• 以/开头可以避免递归匹配

• 以/结尾指定匹配目录

• !声明，为不匹配指定文件或者目录,即不被忽略

Glob模式类似于shell使用的简化正则表达式:

• 星号(*)可以匹配0个或者多个字符
• [abc]可以匹配中括号中的任意一个字符
• 问号(?)匹配任意一个字符
• [0-9]可以匹配0到9之间的任意一个数字
• 使用两个星号可以匹配多级目录，例如a/**/z,可以匹配a/z,a/b/z,a/b/c/z等等

下面是一个.gitignore的例子：

# 忽略所有的.a格式的文件
*.a
# 但是要追踪lib.a，即lib.a不会被忽略，尽管上面已经忽略了所有的.a文件，这就是!的作用
!lib.a
# 只忽略当前文件夹下面的TODO文件，而不会递归子文件夹
/TODO
#忽略所有build文件夹下面的文件和文件夹
build/
#忽略doc文件夹下面的.txt文件，但是不会递归子文件夹下面的.txt
doc/*.txt
# 递归忽略doc文件夹下面的所有的.pdf文件
doc/**/*.pdf