Ah, good call. I have a few questions though:

Will passing the path to the credential fill command (https://github.com/github/git-lfs/pull/554/files#diff-1eed123d34cdc2b60cc1a63521a9ca88R20) cause any problems for those of us without useHttpPath enabled? I don't think so, but I'll setup my laptop to use the osxkeychain helper instead of boxen's to see firsthand.

Do you by chance know what path git uses for pushes and pulls? We don't want end users to have to enter their password again for /{user}/{repo}.git/info/lfs/objects when they've already entered it for /{user}/{repo}.git.

EDIT: Found it. Git doesn't try to do anything intelligent.

git clone https://github.com/github/git-lfs-test
Cloning into 'git-lfs-test'...
Username for 'https://github.com/github/git-lfs-test': 

So, I think this should attempt to use the same path that the remote uses IF apiUrl's scheme and host matches the remote.

$ git remote show origin
* remote origin
  Fetch URL: https://github.com/github/git-lfs-test
  Push  URL: https://github.com/github/git-lfs-test

In this case, getCreds() should pass a path of "github/git-lfs-test" so that it's using the same user/pass as the Git repo.

I think this needs to strip the leading / from the path:

Downloading droidtocat.gif (24.65 KB)
trace git-lfs: run_command: 'git' config -l
trace git-lfs: run_command: 'git' config -l -f .git/config
Username for 'https://github.com//technoweenie/glowing-octo-lana.git/info/lfs/objects':

The Username prompt looks correct here:

$ echo "protocol=https\nhost=github.com\npath=technoweenie/glowing-octo-lana.git/info/lfs/objects" | git credential fill 
Username for 'https://github.com/technoweenie/glowing-octo-lana.git/info/lfs/objects':

Added trimming the leading slash, so you get this now:

$ git clone https://github.com/technoweenie/glowing-octo-lana
Downloading droidtocat.gif (24.65 KB)
Username for 'https://github.com/technoweenie/glowing-octo-lana.git/info/lfs/objects'

Good idea on re-using the base remote URL, I'll work on that

Patch will now use the git remote's credentials if possible.

$ git clone https://github.com/technoweenie/glowing-octo-lana
Downloading droidtocat.gif (24.65 KB)
Password for 'https://clareliguori@github.com/technoweenie/glowing-octo-lana':

This looks great. There are a couple more things:

1. The code to set the auth from the git remote is directly copied from earlier in the function. It could be extracted into a small, private helper function. I'll probably just make a small refactoring PR after merging this.
2. I'd really like new tests for this. Unfortunately, we don't have adequate credential tests at ALL. So I'll probably tackle this on my own.

This will likely make it into Git LFS v0.6.0, and a v0.5.5 if another bug fix release is necessary. Thanks for sending this patch!

Thanks again for the patch. I made a private helper and added some shell tests in #561.