Symbols .pdb formatting issue?

[ashtonian]

So I couldn't get symbols to work and I put a test on MyGet to see if I could get it to work there, and it did. I began digging and eventually compared the .pdb files. There were a couple of things different but most notably was the SRCSRV section. Testing srcsrv locally seemed to indicate everything fine, it was producing accessible urls with source files. The variable composition section is different even though they are almost identical.

Original Section produced by Klondike (Doesn't Work):

VERSION=2
INDEXVERSION=2
VERCTRL=NuGet
DATETIME=10/31/2016 8:53:42 PM
SRCSRV: variables ------------------------------------------
SRCSRVVERCTRL=http
NUGET=https://packages.our-url.com/api/source
HTTP_EXTRACT_TARGET=%NUGET%/%var4%/%var2%/%var5%
SRCSRVTRG=%HTTP_EXTRACT_TARGET%
SRCSRVCMD=

Manually updated based on MyGet pdb that does work:

VERSION=2
INDEXVERSION=2
VERCTRL=http
DATETIME=10/31/2016 8:53:42 PM
SRCSRV: variables ------------------------------------------
SRCSRVVERCTRL=http
SRCSRVTRG=https://packages.our-url.com/api/source/%var4%/%var2%/%var5%
SRCSRVCMD=

I have submitted a PR with a proposed change, but its a hack - I have no idea why the "fix" works. I can't find any documentation on what the value should be or how they are being used and by what.