Inspired by these instructions, I followed these steps:
Then you need to configure git to be able to find and invoke meld. If you’re using the git bash shell, this can be done with these commands:
PATH=$PATH:/c/python26 git config --global merge.tool meld git config --global mergetool.meld.path /c/Users/andarno/Downloads/meld-1.5.2/bin/meld
Of course you may want to set your PATH to include Python permanently rather than the above command which only works for your active window. The two git config commands have a persistent effect already, however.
Finally, you’re now ready to use meld to resolve merge conflicts. I haven’t found a way to get “git gui” to invoke the merge tool correctly, but this command from the git bash shell works great: