Process of updating a local branch from another with tracking

[Robert Dailey <rcdailey.lists@gmail.com>]

I have the following alias defined:
sync = "!f() { cbr=$(git rev-parse --abbrev-ref HEAD); git co $1 &&
git pull && git co $cbr && git rebase $1; }; f"

The goal is to basically update a local branch which tracks a branch
on a remote, and then rebase my local topic branch onto that updated
local branch.

I do this instead of just rebasing onto origin/master. Example:

git checkout master
git pull --rebase origin master
git checkout topic1
git rebase master

I could do this instead but not sure if it is recommended:

git checkout topic1
git fetch
git rebase origin/master

Any thoughts on the alias I created? I'm a Windows user and still new
to linux stuff, so if it sucks or could be simplified just let me
know.

And as a secondary question, just curious what people think about
rebasing onto a remote tracking branch. When I do merges I usually
refer to the remote branch, but during rebase I use the local branch
instead, but I don't know if there is any functional reason to not
skip the local branch and go straight to the remote tracking branch
(it saves a step).