what is git pull origin master --allow-unrelated-histories code example

Example 1: fatal: refusing to merge unrelated histories

git pull --allow-unrelated-histories

Example 2: git unrelated histories

git pull origin branchname --allow-unrelated-histories

Example 3: git unrelated histories

git merge upstream/master --allow-unrelated-histories

Example 4: refusing to merge unrelated histories git

I think its get sorted after using below command
>git pull --allow-unrelated-histories