TLDR: Visit the git-commit-ectomy guide: http://pages.charlesreid1.com/git-commit-ectomy
Consider the following completely hypothetical scenario.
Suppose you've been working for a while on your latest invention, a brand-new whiz-bang command line tool that's fast and solves an important problem and you're chugging your way to the finish line.
As part of preparing to release your software tool, you add some tests, because that's what you do.
Those tests require some data, so you add a few test data sets, a few hundred kilobytes each, nothing fancy.
Then one day, the intern (who is just trying to be helpful by adding a new test) slips in a 70 MB test data set, and slips it in with a string of commits that somehow get incorporated into the master branch.
(Side note: you turned on branch protection to prevent this whole mess, didn't you? Didn't you?? 'Course you did. This is all just a hypothetical scenario.)
Now, the situation is complicated: there are several open pull requests and active branches, and a non-trivial amount of history that's been added since the time the large test data set was accidentally added.
The intern apologizes profusely and promises to bring in donuts every day next week. But the damage is done.
The intern, a git novice, pulls out a laptop
and runs a git rm on the files, pushing to the
remote and happily, ignorantly believing the problem
has been solved.
But the intern does not understand how git works. It has a perfect memory, and remembers every file in every commit. Since the problematic first commit that added the large files, git has remembered and will always remember that large file. It's in git's blood. It's what git was designed to do.
Once the intern has been, ahem, moved along, and branch protection has been turned on, it's time to find a git surgeon to perform a git-commit-ectomy to remove the problematic large files from the repository entirely.
Dr. Reid's Patented Git-Commit-Ectomy
If it's a git-commit-ectomy you need, try Dr. Reid's Patented Git-Commit-Ectomy to ease your git commit pains.
Whether you want to keep thing simple and remove a git commit from a single branch, or if you've got multiple branches, Dr. Reid's Patented Git-Commit-Ectomy will get you back on your feet.
Dr. Reid's Patented Git-Commit-Ectomy can handle even the most messy, confused, and tangled git commit history - with a bit of work and a gifted surgeon the git-commit-ectomy can smooth things out and get you feeling right as rain.
Visit the git-commit-ectomy guide: http://pages.charlesreid1.com/git-commit-ectomy