git - How to fast forward a branch to another non-master branch -

i on branch b. when checking out branch a, message behind branch 1 commit.

git checkout switched branch 'a' branch behind 'origin/a' 1 commit, , can fast-forwarded.

but when on own branch, cannot git pull because says not appear repository.

i confused because when git merge a, message date. how can when i'm behind 1 commit?

what can do?

git pull fetch+merge, updates branch you're working on when pulls. references of branches updated, git aware local ref outdated.

# on branch git merge origin/a --ff-only 

this update history latest status of a.