All merge conflicts cause an error, cannot be resolved

Question

Over the last few weeks, any time I get a merge conflict I get a fatal error.

Steps to reproduce:

checkout branch name
git pull origin master

At this point, my VScode would show the conflict(s) in the file and give me the opportunity of which to pick. This has happened for years..

But now, I get this error instead

 * branch            master     -> FETCH_HEAD
fatal: Not possible to fast-forward, aborting.

VScode won't show me the conflict, there appears to be no way to resolve it except for deleting entire branch, creating a new branch from master, then rebuilding all my changes.

There are solutions that may apply in the answers to this question: https://stackoverflow.com/questions/13106179/fatal-not-possible-to-fast-forward-aborting — topsail, Oct 24 '22 at 20:58
I was thinking along the same lines as those that are asking if (somehow) a `ff-only` option has been configured for `pull`. — topsail, Oct 24 '22 at 20:59
Hi Topsail, thank you for posting that, I found that thread before posting this, I tried every item listed, not one helped — Justin Blayney, Oct 24 '22 at 20:59
Do you get the same errors when you do a pull in a terminal (not with "vscode features")? — topsail, Oct 24 '22 at 21:01
I tried both vscode and terminal, my default is to use terminal — Justin Blayney, Oct 24 '22 at 21:02
what happens with `git fetch` followed by `git merge`? or `git pull --no-ff`. Have you inspected your local .git config (s) - there can be more than one! — topsail, Oct 24 '22 at 21:10
git pull --no-ff, gets exact same error as git pull origin master — Justin Blayney, Oct 24 '22 at 21:14
Well sounds like you don't actually have a problem :) It seems you can check your pull configuration with this command `git config pull.ff` and if it responds `only` then you are configured for ff-only pulls. — topsail, Oct 24 '22 at 21:16
After "git merge", "got fetch", if I do git pull --ff-only, now i get "Already up to date" — Justin Blayney, Oct 24 '22 at 21:16
but bitbucket gives me a merge conflict error and wont let me merge — Justin Blayney, Oct 24 '22 at 21:17

score 1 · Answer 1 · answered Oct 24 '22 at 21:23

The message:

fatal: Not possible to fast-forward, aborting.

means that you've told Git to use --ff-only for the merge that occurs as the second step of git pull¹ and that this merge cannot be done as a fast-forward.

There was a bug in Git 2.33 where --ff-only misbehaved in certain cases:

 * "git pull --ff-only" and "git pull --rebase --ff-only" should make
   it a no-op to attempt pulling from a remote that is behind us, but
   instead the command errored out by saying it was impossible to
   fast-forward, which may technically be true, but not a useful thing
   to diagnose as an error.  This has been corrected.
   (merge 361cb52383 jc/fix-pull-ff-only-when-already-up-to-date later to maint).

If you have this version of Git, you should upgrade to 2.34 or later. Your comment implies that you've hit this particular bug.

(Your comment about Bitbucket almost certainly involves something else entirely, and is a Bitbucket issue, not a Git one.)

¹Remember that git pull is a convenience short-cut that means:

run git fetch;
run a second Git command to do something with the commits obtained in step 1.

The default second command is git merge but you can choose git rebase instead. The --ff-only option is an option to git merge and means nothing to git rebase, so git pull won't supply --ff-only to the second command if you choose git rebase (but it is supposed to stop the rebase for that case). Whether git merge supplies --ff-only to the second command if you choose git merge depends on how you configure git pull to operate.

Thank you for the detailed explanation, we have a whole other team that manages this (upgrading git). I will reach out to them — Justin Blayney, Oct 24 '22 at 21:25
Am I assume you mean on the server, my local version of git is 2.37.3 — Justin Blayney, Oct 24 '22 at 21:29
Wherever you got the `fatal` message. The only reason to get that message is when you've chosen `--ff-only` and there's no way to fast-forward, or to encounter the Git 2.33 bug; follow the link to see the details. You could get a *different* error message under various other tricky circumstances, though. — torek, Oct 24 '22 at 21:34

score 0 · Accepted Answer · answered Oct 25 '22 at 14:02

0

steps to fix:

% vi ~/.gitconfig
in vi, type E

in edit screen, Comment out 2 lines

#[pull]

#ff only

Save, everything works

answered Oct 25 '22 at 14:02

Justin Blayney

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All merge conflicts cause an error, cannot be resolved

2 Answers2