No need for indirectionThe export.fld file is the interesting result of this repository for one maven indexa.
With this new commit, running the image will compute and expose directly that result to
be published.
In effect,Prior to this commit, the docker image was only in charge of triggering the
extract_index.sh script. this allows to push a standalone imageThe python script was the orchestrator in our docker registry.charge of downloading
That means all computations are done within the image and then that image
exposes only the result that needs to be published for the lister to consumeindexes, run the docker image and out of the index files retrieved, extract the
resulting export.fld script.
Example use:
```
$ docker volume create maven_index_exporter
$ docker run \
-v maven_index_exporter:/work \
-v /tmp/maven_index_exporter:/publish \
softwareheritage/maven-index-exporter
$ file /tmp/maven_index_exporter/export.fld # on the machine running docker
/tmp/maven_index_exporter/export.fld: UTF-8 Unicode text, with very long lines
```
Related to T3746