from `r2` but exclude the ones reachable from `r1`.
This set operation appears so often that there is a shorthand
for it. When you have two commits `r1` and `r2` (named according
to the syntax explained in SPECIFYING REVISIONS above), you can ask
for commits that are reachable from r2 excluding those that are reachable
from `r2` but exclude the ones reachable from `r1`.
This set operation appears so often that there is a shorthand
for it. When you have two commits `r1` and `r2` (named according
to the syntax explained in SPECIFYING REVISIONS above), you can ask
for commits that are reachable from r2 excluding those that are reachable