This has nothing to do with Beyond Compare, just with learning Git. Instead of googling everything, learn to use the built-in help. Looking at monochrome text in the terminal is a great skill to have and your efficiency will 3x, guaranteed.
Step 1: Simply type git help
Here are the only things Git knows how to do. In the terminal, when you type git help, it will show you this list: clone, init, add, mv, reset, rm, bisect, grep, log, show, status, branch, checkout, commit, diff, merge, rebase, tag, fetch, pull, push
Scan this list and decide which word is the closest to what you are trying to do.
Step 2: Now make a two-word help request
Maybe fetch is what you want; just type git help fetch.
Wow, lots of text! Now you may be a little put off. Be patient! There are two keys to understanding this man page. I'll give two tips and then leave you to explore.
Man pages are sort of long. Sometimes, instead of scrolling, you should search. Type a slash followed by the word you are searching. Now, a quirk: hit Enter once, and then hit 'n' several times. 'Enter' will search for the first occurance of your word. 'n' will search for subsequent occurances.
Learn to read the top few lines.
That's plenty of advice. You now know enough to dig (for years!) through the Git's unusually helpful man pages.