basic question

I have bare repo X, and two clones A and B (basically my work copy and
home copy of same personal files. I use 'git-pull origin' and 'git
push origin master' to sync files).

The same file 'xxx' was modified on A and on B, and committed on both.
In A, trying now 'git-pull origin', I get 'xxx: needs update'.
Which commands do I use now to merge xxx on A ?

Thanks
Yakov