How to deal with this git warning? "Pulling without specifying how to reconcile divergent branches is discouraged"

After a git pull origin master I get the following message:

warning: Pulling without specifying how to reconcile divergent branches is
discouraged. You can squelch this message by running one of the following
commands sometime before your next pull:

  git config pull.rebase false  # merge (the default strategy)
  git config pull.rebase true   # rebase
  git config pull.ff only       # fast-forward only

You can replace "git config" with "git config --global" to set a default
preference for all repositories. You can also pass --rebase, --no-rebase,
or --ff-only on the command line to override the configured default per
invocation.

remote: Enumerating objects: 4, done.
remote: Counting objects: 100% (4/4), done.
remote: Compressing objects: 100% (4/4), done.
remote: Total 4 (delta 0), reused 0 (delta 0), pack-reused 0
Unpacking objects: 100% (4/4), 51.49 KiB | 850.00 KiB/s, done.

Then the pull has been done successfully. But still, I have doubts about this message.
What is the best thing to do in this case?

Solution 1:

In its default mode, git pull is shorthand for git fetch followed by git merge FETCH_HEAD.

When you do a git pull origin master,
git pull performs a merge, which often creates a merge commit. Therefore, by default, pulling from the remote is NOT a harmless operation: it can create a new commit sha that didn’t exist before. This behavior can confuse a user, because what feels like it should be a harmless download operation actually changes the commit history in unpredictable ways.

To avoid this, you need

git pull --ff-only

(or not? read on to see which one fits your requirements)

With git pull --ff-only, Git will update your branch only if it can be “fast-forwarded” without creating new commits. If this can’t be done, git pull --ff-only simply aborts with an error message.

You can configure your Git client to always use --ff-only by default, so you get this behavior even if you forget the command-line flag:

git config --global pull.ff only

Note: The --global flag applies the change for all repositories on your machine. If you want this behaviour only for the repository you're in, omit the flag.

Taken from here

This warning was added in Git 2.27.

This is what the complete warning looks like:

Pulling without specifying how to reconcile divergent branches is discouraged. You can squelch this message by running one of the following commands sometime before your next pull:

git config pull.rebase false     # merge (the default strategy)
git config pull.rebase true      # rebase
git config pull.ff only               # fast-forward only

You can replace "git config" with "git config --global" to set a default preference for all repositories. You can also pass --rebase, --no-rebase, or --ff-only on the command line to override the configured default per invocation.

The warning presents three commands as options, all of these will suppress the warning. But they serve different purposes:

git config pull.rebase false     # merge (the default strategy)

This keeps the default behaviour and suppresses the warning.

git config pull.rebase true      # rebase

This actually commits on top of the remote branch, maintaining a single branch both locally and remotely (unlike the default behaviour where two different branches are involved - one on local and the other on remote - and, to combine the two, a merge is performed).

git config pull.ff only          # fast-forward only

This only performs the pull if the local branch can be fast-forwarded. If not, it simply aborts with an error message (and does not create any commits).

Update:

If you have Git 2.29 or above, you can now set pull.ff to false, true or only to get rid of the warning.

git config pull.ff true

true - This is the default behaviour. Pull is fast-forwarded if possible, otherwise it's merged.

git config pull.ff false

false - Pull is never fast-forwarded, and a merge is always created.

git config pull.ff only

only - Pull is fast-forwarded if possible, otherwise operation is aborted with an error message.

Note: You may wanna keep an eye on VonC's answer here for updates on changes made to this feature in future updates.

Solution 2:

This is a new warning added in Git 2.27:

 * "git pull" issues a warning message until the pull.rebase
   configuration variable is explicitly given, which some existing
   users may find annoying---those who prefer not to rebase need to
   set the variable to false to squelch the warning.

To remove the warning, set one of the suggested values to your preferred default behaviour for git pull if you don't specify behaviour on the command line (using --ff, --no-ff, --ff-only, --rebase). In all cases, git will attempt a fast-forward (What is git fast-forwarding?) merge if possible. The settings control what happens when there are changes in your branch but not present in the remote branch.

  git config pull.rebase false  # merge (the default strategy)

This is the existing default behaviour; set this for no warning, and no change in behaviour; git will merge the remote branch into your local one.

  git config pull.rebase true   # rebase

Here, git will attempt to rebase your changes on top of the remote branch. See When should I use git pull --rebase? for more detail on why you might want that.

  git config pull.ff only       # fast-forward only

If a fast-forward merge is not possible, git will refuse to proceed. As Difference between git pull --rebase and git pull --ff-only quotes:

Refuse to merge and exit with a non-zero status unless the current HEAD is already up-to-date or the merge can be resolved as a fast-forward