git log --pretty=oneline tagA...tagB (i.e. three dots)
If you just wanted commits reachable from tagB but not tagA:
git log --pretty=oneline tagA..tagB (i.e. two dots)
or
git log --pretty=oneline ^tagA tagB
git log --pretty=oneline tagA...tagB (i.e. three dots)
If you just wanted commits reachable from tagB but not tagA:
git log --pretty=oneline tagA..tagB (i.e. two dots)
or
git log --pretty=oneline ^tagA tagB