I have multiple branches which are branched off the master (each in a separate subdirectory).
git checkout [branchYouWantToReceiveBranch]
- checkout branch you want to receive branchgit merge [branchYouWantToMergeIntoBranch]
First, checkout to your Branch3:
git checkout Branch3
Then merge the Branch1:
git merge Branch1
And if you want the updated commits of Branch1 on Branch2, you are probaly looking for git rebase
git checkout Branch2
git rebase Branch1
This will update your Branch2 with the latest updates of Branch1.