Need to reset git branch to origin version

If you haven't pushed to origin yet, you can reset your branch to the upstream branch with:

git checkout mybranch
git reset --hard origin/mybranch

(Make sure that you reference your latest commit in a separate branch, like you mention in your question)

Note that just after the reset, mybranch@{1} refers to the old commit, before reset.

But if you had already pushed, see "Create git branch, and revert original to upstream state" for other options.

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With Git 2.23 (August 2019), that would be one command: git switch.
Namely: git switch -C mybranch origin/mybranch

Example

C:\Users\vonc\git\git>git switch -C master origin/master
Reset branch 'master'
Branch 'master' set up to track remote branch 'master' from 'origin'.
Your branch is up to date with 'origin/master'.

That restores the index and working tree, like a git reset --hard would.

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As commented by Brad Herman, a reset --hard would remove any new file or reset modified file to HEAD.

Actually, to be sure you start from a "clean slate", a git clean -f -d after the reset would ensure a working tree exactly identical to the branch you just reset to.

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This blog post suggests those aliases (for master branch only, but you can adapt/extend those):

[alias]
   resetorigin = !git fetch origin && git reset --hard origin/master && git clean -f -d
   resetupstream = !git fetch upstream && git reset --hard upstream/master && git clean -f -d

Then you can type:

git resetupstream

or

git resetorigin

Assuming this is what happened:

# on branch master
vi buggy.py                 # you edit file
git add buggy.py            # stage file
git commit -m "Fix the bug" # commit
vi tests.py                 # edit another file but do not commit yet

Then you realise you make changes on the wrong branch.

git checkout -b mybranch    # you create the correct branch and switch to it

But master still points to your commit. You want it to point where it pointed before.

Solution

The easiest way is:

git branch --force master origin/master

Another way is:

git checkout master
git reset --soft origin/master
git checkout mybranch

Note that using reset --hard will cause your uncommitted changes to be lost (tests.py in my example).

There is a slightly easier way to do this:

git reset --hard @{u}

@{u} is a shortcut for whatever your tracking branch is, so if you're on master and that tracks origin/master, @{u} points to origin/master.

The advantage of using this is that you don't have to remember (or type out) the full name of your tracking branch. You can also make an alias:

git-reset-origin="git reset --hard @{u}"

which will work regardless of the branch you're currently on.