How do I specify local .gem files in my Gemfile?

Seems bundler can't use .gem files out of the box. Pointing the :path to a directory containing .gem files doesn't work. Some people suggested to setup a local gem server (geminabox, stickler) for that purpose.

However, what I found to be much simpler is to use a local gem "server" from file system: Just put your .gem files in a local directory, then use "gem generate_index" to make it a Gem repository

mkdir repo
mkdir repo/gems
cp *.gem repo/gems
cd repo
gem generate_index

Finally point bundler to this location by adding the following line to your Gemfile

source "file://path/to/repo"

If you update the gems in the repository, make sure to regenerate the index.

This isn't strictly an answer to your question about installing .gem packages, but you can specify all kinds of locations on a gem-by-gem basis by editing your Gemfile.

Specifying a :path attribute will install the gem from that path on your local machine.

gem "foreman", path: "/Users/pje/my_foreman_fork"

Alternately, specifying a :git attribute will install the gem from a remote git repository.

gem "foreman", git: "git://github.com/pje/foreman.git"

# ...or at a specific SHA-1 ref
gem "foreman", git: "git://github.com/pje/foreman.git", ref: "bf648a070c"

# ...or branch
gem "foreman", git: "git://github.com/pje/foreman.git", branch: "jruby"

# ...or tag
gem "foreman", git: "git://github.com/pje/foreman.git", tag: "v0.45.0"

(As @JHurrah mentioned in his comment.)