Suppose there are multiple git branches that are in your local repo. You've done tons of work, eventually committed and pushed. Then, you found you were working at a wrong branch! And pushed changes to a wrong branch remotely too! Ooops...

What to do?

First, see which branch you're on:

$ git branch
  master
  duplicate-target
* remove-tab
  api-integration

You're on branch remove-tab, but you actually should have committed and pushed from branch api-integration. You can revert the commit you did and commit to the correct branch by doing following:

• On the remove-tab branch, do:

$ git log

commit 984d0ccdd9c80941121dfc1e208b25efeb091111
Author: Wendy 

    Add api integration and tests

commit 0909fa4b87ddaa7d08e823f9b02f24c35a9f372a
Author: Eric

    Update server

commit ef78fcb6a1d30955210178772dcc71234c5e4012
Author: Wendy 

    Add new removed tab
  

• Copy the hash that the latest commit this branch should be at and do:

$ git reset 0909fa4b87ddaa7d08e823f9b02f24c35a9f372a

And you'll see

M app/controllers/book_controller.rb
M app/models/post.rb
M app/models/target.rb
M db/schema.rb

• At this point, you're reverted local repo to the state right before you did the wrong commit.
  Now you need to stash all the changes and force push to remote.

$ git stash
$ git push --force

After force push, the branch at remote is reverted to previous state. You're good on remove-tab branch.

• Now onto the branch you should've been on.

$ git checkout api-integration

Pop up stash, commit and push again

$ git stash pop
$ git commit -a
$ git push

You're all set!