Most open source projects seem to use Git, but there are a few which have opted for Mercurial instead, most notably Mozilla projects such as Firefox and Thunderbird. For some inexplicable reason, Mercurial doesn’t show any indications of progress when running commands such as hg clone unless you explicitly enable the progress extension.
Fortunately, you can easily solve this problem by adding the following lines to ~/.hgrc:
[extensions] progress =