Reverse a git fetch

Question

I have a thorough understanding of git, and the difference between pull, fetch, and merge. I have a remote that I track, fetch, and merge with occasionally, let say it's origin/master. What I'm looking to do is reverse the behavior of a 'git fetch'. It sounds goofy, but I want to un-update where my remote tracking branch points, to an older state, the state right before the last fetch. Is this possible?

For example, lets say this is my workflow...

git show origin/master # shows commit abc123  git fetch              # yay i got something!  git show origin/master # shows commit def456 

mystery command goes here so that...

git show origin/master # shows commit abc123 

It's kind of a weird thing to want, but I have a crontab that watches a git repo to detect when there's something to fetch, and I'm having issues debugging the script that performs some actions based on this behavior. Instead of waiting for origin/master to change, I'd like to change it myself so I can debug my script!

Answer 1

You want

git update-ref refs/remotes/origin/master refs/remotes/origin/master@{1}

update-ref wants the full spell on the ref it's updating because it's (much) lower level than the commands that respect ref-naming conventions.