*: rename master branch to main

ci/ci-commitmessage-submodules.sh

@@ -40,7 +40,7 @@ gitdir=$(realpath $(pwd))
 # require a newer git, we could use `git worktree`.
 cp -a ${gitdir} ${tmpd}/workdir
 cd ${tmpd}/workdir
-git log --pretty=oneline origin/master..$HEAD | while read logline; do
+git log --pretty=oneline origin/main..$HEAD | while read logline; do
     commit=$(echo ${logline} | cut -f 1 -d ' ')
     # For merge commits, just check that they're empty (i.e. no conflict
     # resolution was needed). Otherwise, let's just error out. Conflicts should