Git for Windows (MSysGit) or Git Cmd

The following commands in a Command Prompt window will update your .gitconfig to configure GIT use DiffMerge:

C:\> git config --global diff.tool diffmerge
C:\> git config --global difftool.diffmerge.cmd
    "C:/Program\ Files/SourceGear/Common/DiffMerge/sgdm.exe
        \"$LOCAL\" \"$REMOTE\""

C:\> git config --global merge.tool diffmerge
C:\> git config --global mergetool.diffmerge.trustExitCode true
C:\> git config --global mergetool.diffmerge.cmd 
    "C:/Program\ Files/SourceGear/Common/DiffMerge/sgdm.exe
        -merge -result=\"$MERGED\" \"$LOCAL\" \"$BASE\" \"$REMOTE\""

This will also work for the Gitcmd that is offered on the Git website, but not the Git Bash shell.

Note that both of the ....diffmerge.cmd ... lines were wrapped for this document. You can verify your settings with the git config --list command.

The commands above assume that the MSI installer was used to install DiffMerge in the standard location. If you installed DiffMerge from the ZIP package, be sure to adjust the pathname to sgdm.exe accordingly.