ivy:listmodule does not find an existing module - ant

Question

We have our shared Ivy repository on an nginx web server reachable within our intranet.
I configured a url resolver to read from the shared repository and an ssh resolver to write to it, mostly following Jason Grimes' excellent blog post on managing dependencies in non-Java projects.
Now I just successfully published a module to the repository via the ssh resolver.
In my SFTP client I can see the directory structure and files sitting in the directory served by the web server:
com.organization/modulename/ivy-modulename-2.0.1.xml.md5
com.organization/modulename/ivy-modulename-2.0.1.xml.sha1
com.organization/modulename/ivy-modulename-2.0.1.xml
com.organization/modulename/modulename-2.0.1.zip.md5
com.organization/modulename/modulename-2.0.1.zip.sha1
com.organization/modulename/modulename-2.0.1.zip
However, when I execute ivy:listmodule it doesn't seem to find it. Frankly, it doesn't output anything apart from the ivysettings initialization output.
This is the Ant target I am executing:
<!-- ================================
target: check-already-in-repo
Check if the current version of a module already exists in the (shared) repository.
================================ -->
<target name="check-already-in-repo">
<ivy:listmodules resolver="shared" organisation="${ivy.organisation}" module="${ivy.module}" revision="${version}" property="already-in-repo" value="true"/>
<ac:if>
<isset property="already-in-repo"/>
<then>
<echo>${ivy.module} ${version} already exists in the repository.</echo>
<echo>Skipping publishing of ${ivy.module}.</echo>
</then>
</ac:if>
</target>
And this is the only output:
$ ant check-already-in-repo -Dversion=2.0.1 -Divy.organisation=com.organization -Divy.module=modulename
Buildfile: [...]/build.xml
check-already-in-repo:
[ivy:listmodules] :: Apache Ivy 2.4.0-rc1 - 20140315220245 :: http://ant.apache.org/ivy/ ::
[ivy:listmodules] :: loading settings :: file = [...]/build/ivysettings.xml
BUILD SUCCESSFUL
Total time: 0 seconds
I checked the value of ivy.shared.default.root and the corresponding ivy and artifact patterns and they're all matching (I kept them simple).
I tried it with the glob matcher and called ivy:listmodules with organization=*, module=* and revision=*, so it should in every case return something. Which it doesn't.
What do I miss?
Here's the rest of the relevant config:
<ivysettings>
<!-- This file is referenced from multiple projects - DO NOT EDIT! -->
<!-- shared -->
<property name="ivy.shared.default.root" value="http://10.79.1.30/ivy"/>
<property name="ivy.shared.default.ivy.pattern" value="[organisation]/[module]/ivy-[module]-[revision].[ext]"/>
<property name="ivy.shared.default.artifact.pattern" value="[organisation]/[module]/[artifact]-[revision].[ext]"/>
<!-- local -->
<property name="ivy.local.default.root" value="${ivy.default.ivy.user.dir}/local"/>
<property name="ivy.local.default.ivy.pattern" value="${ivy.shared.default.ivy.pattern}"/>
<property name="ivy.local.default.artifact.pattern" value="${ivy.shared.default.artifact.pattern}"/>
<settings defaultResolver="default"/>
<resolvers>
<filesystem name="local">
<ivy pattern="${ivy.local.default.root}/${ivy.local.default.ivy.pattern}" />
<artifact pattern="${ivy.local.default.root}/${ivy.local.default.artifact.pattern}" />
</filesystem>
<!-- read access -->
<url name="shared">
<ivy pattern="${ivy.shared.default.root}/${ivy.shared.default.ivy.pattern}" />
<artifact pattern="${ivy.shared.default.root}/${ivy.shared.default.artifact.pattern}" />
</url>
<!-- write access -->
<ssh name="ssh" host="10.79.1.30" port="22" user="ivy" userPassword="${ivy.ssh.password}" publishPermissions="0664">
<ivy pattern="${ivy.shared.default.ivy.pattern}" />
<artifact pattern="${ivy.shared.default.artifact.pattern}" />
</ssh>
<chain name="default" returnFirst="true">
<resolver ref="local"/>
<resolver ref="shared"/>
</chain>
</resolvers>
</ivysettings>

Answer 1

After executing the Ant target with the -d (debug) option something caught my eye:
$ ant check-already-in-repo -Dversion=2.0.1 -Divy.organisation=com.organization -Divy.module=modulename -d
[...]
[ivy:listmodules] using shared to list all in http://10.79.1.30/ivy/
[ivy:listmodules] HTTP response status: 403 url=http://10.79.1.30/ivy/
[ivy:listmodules] CLIENT ERROR: Forbidden url=http://10.79.1.30/ivy/
[ivy:listmodules] HTTP response status: 403 url=http://10.79.1.30/ivy/
[ivy:listmodules] CLIENT ERROR: Forbidden url=http://10.79.1.30/ivy/
[ivy:listmodules] problem while listing resources in http://10.79.1.30/ivy/ with shared (java.io.IOException: The HTTP response code for http://10.79.1.30/ivy/ did not indicate a success. See log for more detail.)
[ivy:listmodules] java.io.IOException: The HTTP response code for http://10.79.1.30/ivy/ did not indicate a success. See log for more detail.
[...]
It seems for listmodules to work, the web server needs to have directory listings enabled. And indeed, after adding
location /ivy {
autoindex on;
}
to the nginx config and restarting the web server it finally worked as expected!
$ ant check-already-in-repo -Dversion=2.0.1 -Divy.organisation=com.organization -Divy.module=modulename
Buildfile: [...]/build.xml
check-already-in-repo:
[ivy:listmodules] :: Apache Ivy 2.4.0-rc1 - 20140315220245 :: http://ant.apache.org/ivy/ ::
[ivy:listmodules] :: loading settings :: file = [...]/build/ivysettings.xml
[echo] modulename 2.0.1 already exists in the repository.
[echo] Skipping publishing of modulename.
BUILD SUCCESSFUL
Total time: 0 seconds
Hooray! :-)