note, given @ https://github.com/dovecot/core/blob/main/build-aux/git-abi-version-gen

...
if test "${VERSION:-}" != ""; then
  :
elif test -f version; then <---------------
  VERSION="`cat version`"
elif test -e .git; then <---------------
  VERSION="0.0.0"
else
  echo "Cannot determine version number">&2
  exit 1
fi

mangle_version $VERSION

assumes either .git or version exists

if in your workflow you pull a tarball of git head

mkdir -p tmp/
cd tmp/
wget -O main.tar.gz https://github.com/dovecot/core/tarball/main
tar xvf main.tar.gz
cd dovecot*

there's NO

ls -ald .git version
	ls: cannot access '.git': No such file or directory
	ls: cannot access 'version': No such file or directory

which will cause the fail

a local workaround is

_this_release_base="2.4.2"

or

_this_release_base="0.0.0"

then

echo ${_this_release_base} > version
echo ${_this_release_base%.*}.ABIv${_this_release_base##*.} > abi-version

you'll need to do it for pigeonhole if building, as well