uninstall files in chunks of 500.

[rolandwalker]

This is intended to address #2122.

I saved a stat by not calling file.exist?, instead passing the -f flag to rm. I would argue that is (strongly) preferable.

I changed the .run! method to .run (allowing rm to return an error code) purely to make the tests pass. Here, I think this is tolerable but not preferable. We should change it back after ironing out tests.

The test glitch occurs in 'snags permissions on ornery dirs, but returns them afterwords'. In the past, ima_installed_file was never getting deleted. It appears that because the dir above was unreadable, ima_installed_file failed the .exist? test, and was silently skipped. Now that the .exist? is gone, rm is actually attempted (and fails).

Of course, tests are still clean with .run! if the test suite is run under sudo. However, the correct thing should be to update the "snags" test. @phinze, I wasn't entirely sure what you were getting at in "snags", so I didn't alter it.

[phinze]

Ooo good call!

Yeah the tests around pkg uninstall are super stubby since I couldn't come up with a realistic way of making an isolated test. The "best" way would probably for us to create some pkgs with different features to drop in test/support/binaries - but I haven't yet had the time to go down that path.

This looks like a step in the right direction for now. Merging. 🚜