Getting a single file from git stash

Sometimes I do want to keep some local changes, even though stash is such a good way to bury and forget them.
A solution from stackoverflow:

git checkout stash@{0} -- [filename]

Git -- non-fast-forward updates were rejected

I got the following error message:

To prevent you from losing history, non-fast-forward updates were rejected
Merge the remote changes before pushing again.  See the 'Note about
fast-forwards' section of 'git push --help' for details.

Stackoverflow helped, as usual. As I am the sole developer of my can of worms, I just added the '-f' flag. It's nice to do the last commit of the photometry code which I've been working on for the last 3 months.

Git -- fixing a detached head

'fixing' as in 're-attaching'. There's nothing intrinsically wrong with having a detached head.
I returned from the state of detached head this way.

'In Git commits form a directed acyclic graph where each commit points to one or more parent commits'.

Geek language, you're a thing of beauty.