Firstly make sure you're using a decent editor with your git e.g. Atom, VS Code etc.

git config --global core.editor "atom"

To modify a merge commit history, like the merges done by popular online version control systems such as GitLab or Bitbucket:

¢ git rebase --rebase-merges -i HEAD~1

Replace the 1 in the example above with the number of merge commits you wish to rebase with. Remember, merge commits can have a number of commits grouped under them

Please note: The --rebase-merges flag is only available as of git version 2.18 and higher. Check your local git version using git —version and upgrade if necessary

For a complex rebase, like changing the merge history as above, first switch to your branch and then try:

Note: I assume you have already done a git pull --rebase and git pull origin local-branch on the branch you'd like to rebase off

$ git rebase local-branch

or

$ git rebase origin remote-branch

If this doesn't work, switch to your branch and then try:

$ git pull origin remote-branch --rebase