[yocto] tar ball vs. git development questions

[James Abernathy]

I have used both git and the tarball methods of bitbaking projects, all of them derivatives of the examples in the Yocto documentation.  I was having issues using the local clone of the Yocto kernel git repository this weekend.  I had successfully done that before, but I was rebuilding the PC workstation, and getting everything setup and tested some of the meta-intel BSPs to make sure I had everything right.  Cloning the linux-yocto-3.0 repository was successful, but the bakes against it failed. I made sure I had poky-extras setup right, but I still had problems.  To isolate the problem, I changed to building with the tarballs and everything worked fine.

So that got me thinking what are the differences between the 2 methods:

I assume that if I use the tarball method, bitbake, using the recipes,  pulls down files from the online repositories and puts those files into the centralized local download directory ($DL_DIR), allowing reuse instead of re-downloading each time.  The content downloaded for linux-yocto-3.0 is exactly what would be pulled from the local repository if I used a local clone of the git repository for linux-yocto-3.0.
If my assumption above is correct, if I'm not modifying the source code of the kernel (only changing config parameters), then once you've run at least one build with the tarball method, the $DL_DIR directory contains all the files you'll need to build any image with linux-yocto-3.0. So there is no need to have a local clone of the kernel repository for speeding up development.  Am I right?
If I have a successful creation of a bare clone of linux-yocto-3.0.git, how could builds of Edison packages be failing?  That makes me concerned about using git and successfully repeating builds of stable branches like Edison.

Jim A
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