Documentation: Correct `git pull` command for syncing with upstream

[mkrndmane]

While setting up the WordPress development environment for the first time, I followed the documentation step by step.

I forked the wordpress-develop repository, cloned my fork locally, and added the official WordPress repository as the upstream remote.

When I reached the section describing how to synchronize my local repository with upstream, I ran the documented command:

git pull --ff upstream/trunk

Git returned the following error:

fatal: 'upstream/trunk' does not appear to be a git repository
fatal: Could not read from remote repository.

Please make sure you have the correct access rights
and the repository exists.

After troubleshooting, I found that git pull expects the remote name and branch name as separate arguments. The following command works correctly:

git pull --ff upstream trunk

Proposed change

Replace:

git pull --ff upstream/trunk

with:

git pull --ff upstream trunk

This small documentation change would help first-time contributors avoid this confusing error during their initial setup.

I'll attach a screenshot of the error for reference.

[mkrndmane]

Documented command fails to execute.

[mkrndmane]

Failed command & succesfull command

[mukesh27]

Thanks for the issue.

Can you open PR with the changes you want to propose?

Fix the documented git pull command used for syncing with the upstream repository.

The README currently shows:

git pull --ff upstream/trunk

This PR updates it to:

git pull --ff upstream trunk

This matches Git's expected syntax (git pull <remote> <branch>) and avoids the fatal error encountered during the initial repository setup.

Trac ticket: https://core.trac.wordpress.org/attachment/ticket/65540/

## Use of AI Tools

AI assistance: Yes

Tool(s): ChatGPT

Model(s): GPT-5.5

Used for: Assisted in drafting the Trac ticket and Pull Request description. I verified the issue, tested the command locally, and prepared the final documentation change myself.

[mkrndmane]

@mukesh27 I have opened PR & linked to this ticket

[khokansardar]

Patch testing report

Patch / PR tested

• ​https://github.com/WordPress/wordpress-develop/pull/12318
• trunk @ 87a5738363 (README.md change reviewed and verified)

Environment

OS: macOS 26.5.1
git: 2.43.0
Local wordpress-develop checkout

Note

This is a documentation-only change (one line in README.md), so it was validated by reproducing the git behaviour directly rather than via the browser/Docker environment.

Steps

1. Created a throwaway local repo with an upstream remote and a trunk branch (mirroring the setup described in the README).
2. Ran the currently-documented command: git pull --ff upstream/trunk.
3. Ran the command proposed by the PR: git pull --ff upstream trunk.
4. Confirmed the string upstream/trunk appears only once in README.md.

Results

• Reproduce bug (before): pass — git pull --ff upstream/trunk fails with the exact error from the ticket: fatal: 'upstream/trunk' does not appear to be a git repository (exit 1). Git treats upstream/trunk as the repository name.
• Apply fix (after): pass — git pull --ff upstream trunk resolves remote upstream + branch trunk correctly and completes successfully (exit 0).
• Scope check: pass — diff changes exactly one line; upstream/trunk occurs only once in README.md, so no other instance was missed.

Conclusion
PR #12318 corrects the documented sync command from git pull --ff upstream/trunk to git pull --ff upstream trunk, matching Git's git pull <remote> <branch> syntax and eliminating the fatal error first-time contributors hit during setup. The change is minimal, idiomatic, and scoped strictly to the ticket — single line, no behavioural or backward-compatibility impact. Recommend commit.