Fix version file for Docker images

Fixes https://github.com/vector-im/riot-web/issues/11642

scripts/docker-write-version.sh

@@ -2,14 +2,16 @@
 
 set -ex
 
-TAG=$(git describe --dirty --tags)
+TAG=$(git describe --tags)
 BRANCH=$(git rev-parse --abbrev-ref HEAD)
 DIST_VERSION=$TAG
 
 # If the branch comes out as HEAD then we're probably checked out to a tag, so if the thing is *not*
 # coming out as HEAD then we're on a branch. When we're on a branch, we want to resolve ourselves to
 # a few SHAs rather than a version.
-if [ $BRANCH != 'HEAD' ]
+# Docker Hub doesn't always check out the tag and sometimes checks out the branch, so we should look
+# for an appropriately tagged branch as well (heads/v1.2.3).
+if [ $BRANCH != 'HEAD' && $BRANCH != 'heads/v*' ]
 then
     REACT_SHA=$(cd node_modules/matrix-react-sdk; git rev-parse --short=12 HEAD)
     JSSDK_SHA=$(cd node_modules/matrix-js-sdk; git rev-parse --short=12 HEAD)