evolve: document the "if not shouldupdate" block
I missed the "not" in "if not shouldupdate: ... hg.updaterepo()" and
it took a long time for me to realize it's about updating *back* to
the original commit (or to its successor). Let's add a comment to
maybe help the person not make the same mistake.
#!/bin/bash
set -euox pipefail
unset GREP_OPTIONS
NOTOPIC="--config experimental.topic-mode=ignore"
compatbranches=`hg branches --quiet | grep 'mercurial-' | grep -v ':' | sort -n --reverse`
prev='stable'
for branch in $compatbranches; do
hg up $branch
hg merge $prev
hg commit -m "test-compat: merge $prev into $branch"
prev=$branch
done