Excessive output if git is not installed

[ndmitchell]

On a brand new machine (64bit Windows), I downloaded the latest 1.1.2 as a binary and put it on the PATH, ran stack setup, and faced a wall of:

Left C:\Users\Neil\AppData\Roaming\stack\indices\Hackage\git-update\all-cabal-hashes\.git\objects\pack: getDirectoryContents: does not exist (The system cannot find the path specified.)
Did not find .cabal file for Agda-2.5.1 with Git SHA of cb3ed7a8d5df3cd50b497637fc317f020d1bf59d
Left C:\Users\Neil\AppData\Roaming\stack\indices\Hackage\git-update\all-cabal-hashes\.git\objects\pack: getDirectoryContents: does not exist (The system cannot find the path specified.)
Did not find .cabal file for AC-Vector-2.3.2 with Git SHA of 32d97a60969fe6912b33597e7399c407b5f2e39a
Left C:\Users\Neil\AppData\Roaming\stack\indices\Hackage\git-update\all-cabal-hashes\.git\objects\pack: getDirectoryContents: does not exist (The system cannot find the path specified.)
Preparing to install GHC to an isolated location.

This went on for 100's of lines, perhaps even 1000's. Is the Left debug droppings that got left? A problem? Not a problem? It hasn't yet lead to a problem, as far as I can tell... But each install does print out a bunch of:

Did not find .cabal file for unordered-containers-0.2.7.1 with Git SHA of 458a2a10936d8e79d96b021505120d1598311fbe
Left C:\Users\Neil\AppData\Roaming\stack\indices\Hackage\git-update\all-cabal-hashes\.git\objects\pack: getDirectoryContents: does not exist (The system cannot find the path specified.)

[ndmitchell]

Installing git and putting it on the $PATH made the large number of warnings go away. This translates to a poor experience for those without git.

[mgsloan]

Dupe of #2241 , which is resolved on master. It's about to be released as v0.1.2