[Galaxy S 4 Developer Discussion [Developers-Only]] AlaskaLinuxUser:
I know that this thread is a couple months old, but I wanted to answer this questions for others who may stumble across this and wonder what the answer was. There are two ways to solve this issue:

(Taken from my wordpress site, where I answered this question before. Here is the link for the full article: https://thealaskalinuxuser.wordpres...samsung-galaxy-s4-t-mobile-jfltetmo-sgh-m919/ )

"... the problem is that the specified device does not have a github branch that is the correct branch. In this case (The case of my article), it is looking for a branch named mm6.0, but it would possibly take a branch named android-6.0.1_r43. The repo command then lists the available branches. The latest branch available for this github repository of this device is lp5.1.

Now the question is what do we do about it? Well, we have several options, but one that I decided to explore today was to use the ROOMSERVICE_BRANCHES variable and choose another branch, as we see here:

alaskalinuxuser@alaskalinuxuser-HP-Compaq-6715b-FY288UC-ABA:~/Documents/projects/phones/compile/slimroms6$ export ROOMSERVICE_BRANCHES=lp5.1
alaskalinuxuser@alaskalinuxuser-HP-Compaq-6715b-FY288UC-ABA:~/Documents/projects/phones/compile/slimroms6$ breakfast
including vendor/slim/vendorsetup.sh

You’re building on Linux

Breakfast menu… pick a combo:
(—EDITED FOR SPACE—)
46. slim_jfltetmo-userdebug 97. slim_vs985-userdebug
(—EDITED FOR SPACE—)
… and don’t forget the bacon!

Which would you like? [aosp_arm-eng] 46
build/core/product_config.mk:234: *** Can not locate config makefile for product “slim_jfltetmo”. Stop.
Device jfltetmo not found. Attempting to retrieve device repository from SlimRoms Github (http://github.com/SlimRoms).
Found repository: device_samsung_jfltetmo
Checking branch info
Calculated revision: mm6.0
Default revision: android-6.0.1_r43
Using fallback branch: lp5.1
Adding dependency: SlimRoms/device_samsung_jfltetmo -> device/samsung/jfltetmo
Using branch lp5.1 for SlimRoms/device_samsung_jfltetmo
Syncing repository to retrieve project.
Fetching project SlimRoms/device_samsung_jfltetmo
remote: Counting objects: 81, done.
remote: Total 81 (delta 0), reused 0 (delta 0), pack-reused 81
From git://github.com/SlimRoms/device_samsung_jfltetmo
* [new branch] jb4.2 -> github/jb4.2
* [new branch] jb4.3 -> github/jb4.3
* [new branch] kk4.4 -> github/kk4.4
* [new branch] lp5.0 -> github/lp5.0
* [new branch] lp5.1 -> github/lp5.1
Fetching projects: 100% (1/1), done.

Repository synced!
Looking for dependencies
Adding dependencies to manifest
Adding dependency: SlimRoms/device_samsung_qcom-common -> device/samsung/qcom-common
Adding dependency: SlimRoms/hardware_samsung -> hardware/samsung
Adding dependency: SlimRoms/device_samsung_jf-common -> device/samsung/jf-common
Adding dependency: CyanogenMod/android_kernel_samsung_jf -> kernel/samsung/jf
Syncing dependencies
Fetching project Slim

So, the user above [MENTION=6797495]vbajs[/MENTION], needed to choose a "fallback" branch if the actual branch needed did not exist, in that case, the user could have typed:

$ . build/envsetup.sh
$ export ROOMSERVICE_BRANCHES=lollipop
$ brunch jfltexx

And then the old "lollipop" branch (listed under Branches Found in the first output) would be downloaded to be used. This does not mean, however, that the build will be successful or work when done by using this older branch. It simply allows you to sync something that was not on the default branch. This tool is pretty handy if you want to try other branches of something without editing your roomservice files, or as in this case, older branches that need updating to a newer branch for testing purposes.

The second option would be to manually download the needed files and place them directly in the appropriate folders. This is effective, but tedious.

Hope that helps the next guy or gal!

Good luck!