This is a tool to run regression tests over a whole series of
commits. Typical usage:
git checkout <topic branch>
tools/git-regtest experimental
This runs 'make regressiontest' for every single commit between
experimental and HEAD of the topic branch. Very convenient to make
sure not a single commit introduces regressions.
If there are regressions, the tools stops at the commit bringing
in the regression, so you immediately know where to look.