Add Microsoft Authentication helper for macOS

[mjcheetham]

Add the initial version of the Mac Microsoft Authentication Helper using ADAL 2.5.1 via CocoaPods. The pods are statically linked so only a single executable "Microsoft.Authentication.Helper" is required to be distributed with GCM.

Also include a script to create a macOS flat-package (.pkg) to install and configure GCM.

The Objective-C auth helper code is from the initial prototype created by @jamill.

[jrbriggs]

Overall this looks great. A few things to consider.

[jrbriggs]

Do we risk losing this configuration if Git is upgraded, like happens on Windows?

[mjcheetham]

The docs around the Apple package installation system is pretty lacking. From my understanding I've created just a 'flat, component package' rather than a distribution package (containing multiple component packages).

Component packages have only a pre- and postinstall scripts which are run for each installation of the package. Distribution packages include more event scripts in addition to pre/postinstall (first install), such as pre/postupgrade (when a component already exists), pre/postflight (before and after the distribution package, made up of multiple component packages as a whole is installed).

If my understanding is correct (it might not be), then postinstall should be called everytime and thus GCM will be reconfigured each time.

Windows GCM is actually reconfiguring itself each time, AFAIK, because it's always invoking itself as git-credential-manager deploy which goes through and updated all the Git installations' configurations.

[mjcheetham]

After looking at what is required on Windows to correctly 'install' GCM, it it probably a reasonable idea to have the configuration logic sit inside GCM itself (much saner and easier to test C# than setup packages and scripts).

If that is the case, it would therefore also make sense for the configuration logic for macOS to also live inside GCM. I had opted not to do this yet however because 1) need to discuss the problems faced with the rest of the team, and 2) this current method is cheap, cheerful, and (relatively) simple/good enough for now.

Comments?

[nickgra]

Your assessment and understanding of the Apple package installation system matches mine, so I think this works as you expect it to.

I'm torn on if it should live inside the GCM or inside the installer, but I think the postinstall script makes sense for now.

[jrbriggs]

@jamill I would appreciate your eyes on this PR too.

[nickgra]

I'll take a closer look at the obj-c later, but this is looking good.

[nickgra]

This arg parser scares me. Since it's only being called by automation (other than you locally iterating on it to write it of course), can we make this simpler? Maybe just error out if $1 and $2 aren't set correctly?

[nickgra]

Your assessment and understanding of the Apple package installation system matches mine, so I think this works as you expect it to.

I'm torn on if it should live inside the GCM or inside the installer, but I think the postinstall script makes sense for now.

[hi-kumar]

Not sure if this impacts this tool. We had to revert ApexBugger to use ADAL 2.5.1 due to known issue with more recent ADAL releases that can log a non-critical message to stderr. Those messages can be misinterpreted by callers of the executables as critical errors.
ADAL Issue 1362

[mjcheetham]

Thanks for the review @HiKumar-MS! 😃
Ah yes, that's an interesting ADAL bug. Technically the warning messages from ADAL to stderr shouldn't get in the way of GCM or Git, but I've downgraded anyway as it could appear as noise in the terminal for users non-the-less, which is ugly.

[jrbriggs]

This looks good to me now. Were you able to test with VFS for Git to make sure the new way we install fixes the issue with Git not finding credential-manager when invoked from GVFS.Mount?

[nickgra]

Looks good now after making the changes. I'm running it now and it seems to be working well!