src/GitWorkingCopy.php
public function isAhead(): bool
    {
        if (! $this->isTracking()) {
            throw new GitException('Error: HEAD does not have a remote tracking branch. Cannot check if it is ahead.');
        }

        $mergeBase = $this->run('merge-base', ['@', '@{u}']);
        $localSha = $this->run('rev-parse', ['@']);
        $remoteSha = $this->run('rev-parse', ['@{u}']);
        return $mergeBase === $remoteSha && $localSha !== $remoteSha;
    }
public function isAhead(): bool
    {
        if (! $this->isTracking()) {
            throw new GitException('Error: HEAD does not have a remote tracking branch. Cannot check if it is ahead.');
        }

        $mergeBase = $this->run('merge-base', ['@', '@{u}']);
        $localSha = $this->run('rev-parse', ['@']);
        $remoteSha = $this->run('rev-parse', ['@{u}']);
        return $mergeBase === $remoteSha && $localSha !== $remoteSha;
    }
Returns whether HEAD is ahead of its remote tracking branch.

If this returns true it means that commits are present locally which have
not yet been pushed to the remote.