How to query the version of a file?

Hi,

I have a standalone repository.
File a.cpp has 3 versions.
For example, I checked out version2(HEAD^).

git checkout HEAD^ a.cpp

After a few days, I forget which version I have checked out.
Is there a git command that can query which version is checked out?
"git status" will show there is "changes to be committed", but with no
the version information.
Thank you!

Best regards,
Halley