github merge origin and master repository

I have main repository at github. I have created a fork. I created a branch and made some changes and committed/pushed on github. Now I need to merge main repository and my branch. How can I merge both. I have created clone of main repositroy. When i try to do

git pull origin branchname

I get

  0 [main] us 0 init_cheap: VirtualAlloc p开发者_如何学JAVAointer is null, Win32 error 487

AllocationBase 0x9A0000, BaseAddress 0x9E0000, RegionSize 0x140000, State 0x2000

C:\Program Files (x86)\Git\bin\sh.exe: * Couldn't reserve space for cygwin's h eap, Win32 error 0

Please suggest how can I merge both ?

I think the workflow is something like this:

git clone http://remote rep here
... Do work ...
git branch temp
git checkout temp
git pull http://remote rep here
git checkout master
git merge temp