[git] Checkout another branch when there are uncommitted changes on the current branch

Most of the time when I try to checkout another existing branch, Git doesn't allow me if I have some uncommitted changes on the current branch. So I'll have to commit or stash those changes first.

However, occasionally Git does allow me to checkout another branch without committing or stashing those changes, and it will carry those changes to the branch I checkout.

What is the rule here? Does it matter whether the changes are staged or unstaged? Carrying the changes to another branch doesn't make any sense to me, why does git allow it sometimes? That is, is it helpful in some situations?

If the new branch contains edits that are different from the current branch for that particular changed file, then it will not allow you to switch branches until the change is committed or stashed. If the changed file is the same on both branches (that is, the committed version of that file), then you can switch freely.

Example:

$ echo 'hello world' > file.txt
$ git add file.txt
$ git commit -m "adding file.txt"

$ git checkout -b experiment
$ echo 'goodbye world' >> file.txt
$ git add file.txt
$ git commit -m "added text"
     # experiment now contains changes that master doesn't have
     # any future changes to this file will keep you from changing branches
     # until the changes are stashed or committed

$ echo "and we're back" >> file.txt  # making additional changes
$ git checkout master
error: Your local changes to the following files would be overwritten by checkout:
    file.txt
Please, commit your changes or stash them before you can switch branches.
Aborting

This goes for untracked files as well as tracked files. Here's an example for an untracked file.

Example:

$ git checkout -b experimental  # creates new branch 'experimental'
$ echo 'hello world' > file.txt
$ git add file.txt
$ git commit -m "added file.txt"

$ git checkout master # master does not have file.txt
$ echo 'goodbye world' > file.txt
$ git checkout experimental
error: The following untracked working tree files would be overwritten by checkout:
    file.txt
Please move or remove them before you can switch branches.
Aborting

A good example of why you WOULD want to move between branches while making changes would be if you were performing some experiments on master, wanted to commit them, but not to master just yet...

$ echo 'experimental change' >> file.txt # change to existing tracked file
   # I want to save these, but not on master

$ git checkout -b experiment
M       file.txt
Switched to branch 'experiment'
$ git add file.txt
$ git commit -m "possible modification for file.txt"

The correct answer is

git checkout -m origin/master

It merges changes from the origin master branch with your local even uncommitted changes.

You have two choices: stash your changes:

git stash

then later to get them back:

git stash apply

or put your changes on a branch so you can get the remote branch and then merge your changes onto it. That's one of the greatest things about git: you can make a branch, commit to it, then fetch other changes on to the branch you were on.

You say it doesn't make any sense, but you are only doing it so you can merge them at will after doing the pull. Obviously your other choice is to commit on your copy of the branch and then do the pull. The presumption is you either don't want to do that (in which case I am puzzled that you don't want a branch) or you are afraid of conflicts.

I have faced the same question recently. What I understand is, if the branch you are checking in has a file which you modified and it happens to be also modified and committed by that branch. Then git will stop you from switching to the branch to keep your change safe before you commit or stash.

In case you don't want this changes to be committed at all do git reset --hard.

Next you can checkout to wanted branch, but remember that uncommitted changes will be lost.