README.md

Reference

http://git-scm.com/docs

http://git-scm.com/docs/gitignore

Within one level of precedence, the last matching pattern decides the outcome.

Patterns read from the command line for those commands that support them.
Patterns read from a .gitignore file in the same directory as the path, or in any parent directory (up to the top-level of the working tree), with patterns in the higher level files being overridden by those in lower level files down to the directory containing the file. These patterns match relative to the location of the .gitignore file. A project normally includes such .gitignore files in its repository, containing patterns for files generated as part of the project build.
Patterns read from $GIT_DIR/info/exclude.
Patterns read from the file specified by the configuration variable core.excludesFile.

The pattern hello.* matches any file or folder whose name begins with hello.. If one wants to restrict this only to the directory and not in its subdirectories, one can prepend the pattern with a slash, i.e. /hello.*; the pattern now matches hello.txt, hello.c but not a/hello.java.
The pattern doc/frotz and /doc/frotz have the same effect in any .gitignore file. In other words, a leading slash is not relevant if there is already a middle slash in the pattern.