[rethab]

Assuming that the repo was this big in the beginning, I wonder why the ever migrated to git (I'm assuming they did, because they can tell how long it takes to checkout). At least when somebody "tries" do the migration, wouldn't they realize that maybe git is not the right tool for them? Or did they actually migrate and then work with "git status" that take 10 minutes for some time until they realize they may need to change something?

Also, it would have been interesting if the article mentioned whether they tried other approaches taken by facebook (mercurial afaik) or google.

[xearl]

To me it sounds like these numbers are from a migration-in-progress. So they are trying, but instead of giving up and saying "not the right tool for us" they are trying to improve the tool.

[becarefulyo]

Because of the productivity benefits of using public tools instead of internal ones. Devs are more familiar with them, more documentation and examples, morale benefit because skills are transferable to other jobs, etc.