Install Meld from their webpage http://meldmerge.org/
I had to tell git where it was:
git config --global merge.tool meld
git config --global diff.tool meld
If using windows 8 and 10 use the following
git config --global mergetool.meld.path "/c/Program Files (x86)/meld/meld.exe"
git config --global difftool.meld.path "/c/Program Files (x86)/meld/meld.exe"
Else use
“C:\Program Files (x86)\Meld\meld\meld.exe” for the path
If you don't want the terminal to prompt you to open with the meld difftool or mergetool we will need to disable the prompt
git config --global difftool.prompt false
git config --global mergetool.prompt false
And that seems to work. Both merging and diffing with “git difftool” or “git mergetool”
Thanks!