I have downloaded AOSP master branch using repo.
But now I want to switch that workspace to any previous Android 11 or 10 before starting to make any changes in the workspace.
I am issuing the following commands but could not do that.

$ git init
$ git remote update
$ git fetch
$ git fetch --all
$ git checkout android-11.0.0_r48
error: pathspec 'android-11.0.0_r48' did not match any file(s) known to git.

and when I want to see the list of branches it displayed nothing.
$ git branch


Note: I downloaded the source using repo commands. Couldn't I switch to another branch using git. If so how to switch to another existing branch, avoiding complete download.

Anybody please help.

1) I don't see git clone among your git commands. What remote repository are you tracking?

2) android-11.0.0_r48 is just a tag that refers to a commit, not at the tip of any named branch. By checking it out you're detaching HEAD at it. See DETACHED HEAD in the git-checkout man page.

Sorry Shruggy,

I used these following commands to download the master branch of Android Open Source Project

Now I want to switch from master branch to Android 11/10/9 in the same workspace directory.
I have not made any changes or initiated any compilation tasks in that directory I downloaded.
What I have to do
1)to avoid downloading all the files from the beginning for the Android versions I want to switch and
2)to download only the required missing files
3)the non relevant files already available if any as residue after switching should not result errors in compilation or the final output files.

Do the following commands sufficient for my needs?

Please reply.