ignoreit is a utility to produce declarative .gitignore specifications that can be used to generate actual .gitignore files. In fact, this .gitignore was produced like this:

ignoreit add Go
ignoreit generate

The first command produces a schema .ignoreit.yml that abstracts the details of a set of .gitignore patterns into a human readable specification. It takes this form:

sources:
- repo: github/gitignore
  branch: master
  entries:
  - Go
- repo: whoshuu/gitignore
  branch: develop
  entries:
  - C++
  - Python 
custom:
- .custompattern
- .anothercustompattern
schema_version: 1

The second command takes this specification and generates a corresponding .gitignore file from it.

Both files should be checked into source control. Only the first should be manually edited via ignoreit, and the second is simply an artifact of changing the schema.

You can install the ignoreit binary like how you would install any Go program:

go get github.com/whoshuu/ignoreit

Since the dependencies are vendored, this should pull in a single package and binary in your ${GOPATH}/bin called ignoreit.

In addition to ignoreit add and ignoreit generate, there is ignoreit remove. This will remove the patterns specified in the argument.

Both add and remove take an arbitrary number of arguments, so multiple entries can be specified at once:

ignoreit add Go CMake C++ Python
ignoreit remove CMake C++

These commands take --repo and --branch flags for specifying the source repository and branch to use for pulling down .gitignore entries. By default these are github/gitignore and master respectively.

Finally, ignoreit generate should be run any time changes are made to .ignoreit.yml. This command takes no arguments and simply inflates the specification into an appropriate .gitignore.