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Editorial Team
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Asked: 2026-05-29T15:05:54+00:00

On a git/github project I am working on a branch. Upon a push, it

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On a git/github project I am working on a branch. Upon a push, it said the following:

git push
To git@github.com:...
 ! [rejected]        master -> master (non-fast-forward)
error: failed to push some refs to 'git@github.com:...'
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.

I tried to fix this problem and upon Googleing I came up with this line:

git push --mirror

I issued the following command and now it seems that I have deleted a lot of branches from the server. 

Total 0 (delta 0), reused 0 (delta 0)
To git@github.com:...
 - [deleted]         develop
 + 797beee...bafbc50 master -> master (forced update)
 - [deleted]         milestone
 - [deleted]         robot
 - [deleted]         strategy
 * [new branch]      origin/HEAD -> origin/HEAD
 * [new branch]      origin/develop -> origin/develop
 * [new branch]      origin/master -> origin/master
 * [new branch]      origin/milestone -> origin/milestone
 * [new branch]      origin/robot -> origin/robot
 * [new branch]      origin/robot_simulator -> origin/robot_simulator
 * [new branch]      origin/strategy -> origin/strategy
 * [new branch]      origin/vision -> origin/vision

Can you tell me what has happened and how can I undo the change I made? (in case I deleted those branches)

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1 Answer

  1. Editorial Team

    You pushed to the default push target, git@github.com. This means, that git@github.com was a remote in you source repo.

    That implies, that the refs deleted from the server would still be in the remote locally after the push. Do not update the remotes (!).

    Verify this by doing

    git branch -a

    on the side you pushed from (local).

    It will probably show the refs that were deleted from the remote server.

    [to be continued]

    You could do something like:

    for-each-ref refs/remotes/origin | while read sha type name
do 
    git branch "rescue_$(basename "$name")" "$sha"
done

    to recover the branches locally. They will be named prefixed with rescue_ just as a precaution (in case you get funny or conflicting ref names).

    Replace origin with the name of your remote

    Test script

    In case you want to test the procedure in a controlled environment, here is my approach condensed to minimum steps (execute in an empty dir, e.g. /tmp/work)

    git init A; (cd A; touch test; git add test; git commit -m initial; git branch test1; git branch test2; git branch test3)
git clone A B
(cd B; git push --mirror origin; git branch -a)
cd A
git for-each-ref refs/remotes/origin | while read sha type name; do git branch "rescue_$(basename "$name")" "$sha"; done
git branch -a

    Note how in this version, I cd into A – which would be your github repo. You could git clone --mirror git@github.com:... local_rescue in order to get a suitable local version of that.

    I recommend you play around getting to terms with the procedure before trying it out. It never hurts to backup your repositories along the way.

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