Why can I not switch branches?

I'm trying to switch branches in git but I'm getting this error message:

error: you need to resolve your current index first

I'm using git under xcode4

git status
# On branch DateCode
# Unmerged paths:
#   (use "git reset HEAD <file>..." to unstage)
#   (use "git add/rm <file>..." as appropriate to mark resolution)
#
#   both modified:      Whereami.xcodeproj/project.xcworkspace/xcuserdatauser.xcuserdatad/UserInterfaceState.xcuserstate
#
no changes added to commit (use "git add" and/or "git commit -a")
Frappuccinos-MacBook-Pro:whereami

Try this if you don't want any of the merges listed in git status:

git reset --merge

This resets the index and updates the files in the working tree that are different between <commit> and HEAD, but keeps those which are different between the index and working tree (i.e. which have changes which have not been added).

If a file that is different between <commit> and the index has unstaged changes -- reset is aborted.

More about this - https://www.techpurohit.com/list-some-useful-git-commands & Doc link - https://git-scm.com/docs/git-reset

You end up with both modified in the output of git status if there were conflicts produced by a merge. git isn't letting you change branch until you've resolved these conflicts. If you edit that file, you should see some conflict markers in it - there's a guide to resolving those conflicts in the git manual. (Since kernel.org is currently down, you can find that guide here instead.)

Alternatively, if you think the merge was a mistake, you could undo it with: git reset --merge

If you don't care about the changes that git says are outstanding, then you can do a force checkout.

git checkout -f {{insert your branch name here}}

I got this message when updating new files from remote and index got out of whack. Tried to fix the index, but resolving via Xcode 4.5, GitHub.app (103), and GitX.app (0.7.1) failed. So, I did this:

git commit -a -m "your commit message here"

which worked in bypassing the git index.

Two blog posts that helped me understand about Git and Xcode are: