smerge is a command line tools for Sublime Merge. To make this tools available in your command line, you have to symlink it. Here’s the command on how to do it for macOS:
ln -s "/Applications/Sublime Merge.app/Contents/SharedSupport/bin/smerge" /usr/local/bin/smerge
That’s it. After this, you can easily browse your repo in Sublime Merge just by typing
smerge in your CLI.
For Windows or Linux, you can check Sublime Merge’s docs.