checkout: clarify "up to date with origin/" uses local remote-tracking ref

[Jesko Schwarzer <jesko@schwarzers.de>]

Hello together,

this is my first post. I am using git*version 2.43.0* on Ubuntu 24.04LTS 
and have an UX proposal:

When I run git checkout master on a branch that tracks origin/master, 
Git often prints:

Your branch is up to date with 'origin/master'.

I naively read this as "my branch matches the current state of the 
remote repository." In practice, origin/master here is only the local 
remote-tracking ref; it is not refreshed unless I run fetch/pull. If the 
remote has moved on since my last fetch, the message can still be "up to 
date" while git pull immediately brings new commits (fast-forwarding 
origin/master and then master).
So the comparison is correct relative to the cached 
refs/remotes/origin/master, but the wording is easy to *misread *as "I 
just verified against the server."

Would the project consider one of the following?
     1. *Clearer messaging*, e.g. indicating that the comparison is 
against the last-known origin/<branch> (or similar wording that does not 
imply a live remote check).
     2. *Optional context* when available (e.g. from reflog or last 
fetch time), so users know how stale the origin/* ref might be — if that 
is technically and policy-wise acceptable.

I understand Git deliberately avoids implicit network access on 
checkout; the issue is only that the status text does not make the 
"local remote-tracking ref" semantics obvious to everyone.

Thanks for maintaining Git,
mit freundlichen Grüßen/Best regards
/Jesko