Represents an installed gem. This is used for dependency resolution.
Installed sources sort before all other sources
# File rubygems/source/installed.rb, line 14
def <=> other
case other
when Gem::Source::Git,
Gem::Source::Lock,
Gem::Source::Vendor then
-1
when Gem::Source::Installed then
0
when Gem::Source then
1
else
nil
end
end