file size check on pom.xml (or thing specified by --file opt) should only apply to regular files (patch attached)

/tmp/mtmp2$ echo $M2_HOME
/usr/local/maven-2.0.4
/tmp/mtmp2$ type -all mvn
mvn is /usr/local/maven-2.0.4/bin/mvn
/tmp/mtmp2$ rm -fr ~/.m2/repository/org/apache/maven/plugins/maven-idea-plugin
/tmp/mtmp2$ cat /tmp/dummy-pom.xml
<?xml version="1.0" ?>
<project>
  <modelVersion>4.0.0</modelVersion>
  <groupId>foo.bar.baz</groupId>
  <artifactId>fooshizzle</artifactId>
  <name>Dummy Project for Retrieving and Installing maven-idea-plugin</name>
  <version>does-not-matter</version>
  <build>
    <plugins>
      <plugin>
        <groupId>org.apache.maven.plugins</groupId>
        <artifactId>maven-idea-plugin</artifactId>
      </plugin>
    </plugins>
  </build>
</project>
/tmp/mtmp2$ cat /tmp/dummy-pom.xml | mvn --file /dev/stdin validate
[INFO] Scanning for projects...
[INFO] ------------------------------------------------------------------------
[ERROR] FATAL ERROR
[INFO] ------------------------------------------------------------------------
[INFO] Error building POM (may not be this project's POM).


Project ID: unknown

Reason: The file /dev/stdin you specified has zero length.


[INFO] ------------------------------------------------------------------------
[INFO] Trace
org.apache.maven.reactor.MavenExecutionException: The file /dev/stdin you specified has zero length.
	at org.apache.maven.DefaultMaven.getProjects(DefaultMaven.java:365)
	at org.apache.maven.DefaultMaven.doExecute(DefaultMaven.java:278)
	at org.apache.maven.DefaultMaven.execute(DefaultMaven.java:115)
	at org.apache.maven.cli.MavenCli.main(MavenCli.java:256)
	at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
	at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:39)
	at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:25)
	at java.lang.reflect.Method.invoke(Method.java:585)
	at org.codehaus.classworlds.Launcher.launchEnhanced(Launcher.java:315)
	at org.codehaus.classworlds.Launcher.launch(Launcher.java:255)
	at org.codehaus.classworlds.Launcher.mainWithExitCode(Launcher.java:430)
	at org.codehaus.classworlds.Launcher.main(Launcher.java:375)
Caused by: org.apache.maven.project.ProjectBuildingException: The file /dev/stdin you specified has zero length.
	at org.apache.maven.DefaultMaven.getProject(DefaultMaven.java:510)
	at org.apache.maven.DefaultMaven.collectProjects(DefaultMaven.java:447)
	at org.apache.maven.DefaultMaven.getProjects(DefaultMaven.java:351)
	... 11 more
[INFO] ------------------------------------------------------------------------
[INFO] Total time: < 1 second
[INFO] Finished at: Wed Jun 21 10:54:28 EDT 2006
[INFO] Final Memory: 1M/2M
[INFO] ------------------------------------------------------------------------
/tmp/mtmp2$

/tmp/mtmp2$ export M2_HOME=/tmp/maven-2.0.4-patched
/tmp/mtmp2$ export PATH=${M2_HOME}/bin:$PATH
/tmp/mtmp2$ type -all mvn
mvn is /tmp/maven-2.0.4-patched/bin/mvn
mvn is /usr/local/maven-2.0.4/bin/mvn
/tmp/mtmp2$ 
/tmp/mtmp2$ rm -fr ~/.m2/repository/org/apache/maven/plugins/maven-idea-plugin
/tmp/mtmp2$ 
/tmp/mtmp2$ cat /tmp/dummy-pom.xml 
<?xml version="1.0" ?>
<project>
  <modelVersion>4.0.0</modelVersion>
  <groupId>foo.bar.baz</groupId>
  <artifactId>fooshizzle</artifactId>
  <name>Dummy Project for Retrieving and Installing maven-idea-plugin</name>
  <version>does-not-matter</version>
  <build>
    <plugins>
      <plugin>
        <groupId>org.apache.maven.plugins</groupId>
        <artifactId>maven-idea-plugin</artifactId>
      </plugin>
    </plugins>
  </build>
</project>
/tmp/mtmp2$ 
/tmp/mtmp2$ cat /tmp/dummy-pom.xml | mvn --file /dev/stdin validate
[INFO] Scanning for projects...
[INFO] ----------------------------------------------------------------------------
[INFO] Building Dummy Project for Retrieving and Installing maven-idea-plugin
[INFO]    task-segment: [validate]
[INFO] ----------------------------------------------------------------------------
[INFO] artifact org.apache.maven.plugins:maven-idea-plugin: checking for updates from central
Downloading: http://my.mvn.proxy.server/maven2Proxy/repository/org/apache/maven/plugins/maven-idea-plugin/2.0/maven-idea-plugin-2.0.pom
2/2K
2K downloaded
Downloading: http://my.mvn.proxy.server/maven2Proxy/repository/org/apache/maven/plugins/maven-idea-plugin/2.0/maven-idea-plugin-2.0.jar
4/37K
8/37K
12/37K
16/37K
20/37K
24/37K
28/37K
32/37K
36/37K
37/37K
37K downloaded
[INFO] No goals needed for project - skipping
[INFO] ------------------------------------------------------------------------
[INFO] BUILD SUCCESSFUL
[INFO] ------------------------------------------------------------------------
[INFO] Total time: < 1 second
[INFO] Finished at: Wed Jun 21 11:05:07 EDT 2006
[INFO] Final Memory: 1M/3M
[INFO] ------------------------------------------------------------------------
/tmp/mtmp2$

...
    mvn --file /dev/stdin validate <<EOF
<project>
  <modelVersion>4.0.0</modelVersion>
  <groupId>foo.bar.baz</groupId>
  <artifactId>fooshizzle</artifactId>
  <name>Dummy Project for Retrieving and Installing ${plugin_name}</name>
  <version>does-not-matter</version>
  <build>
    <plugins>
      <plugin>
        <groupId>${plugin_group_id}</groupId>
        <artifactId>${plugin_name}</artifactId>
        ${plugin_version_elem}
      </plugin>
    </plugins>
  </build>
</project>
EOF
...

$ make -f /dev/stdin <<EOF
> all:
>       @echo "hello from stdin"
> EOF
hello from stdin

$ ant -buildfile /dev/stdin <<EOF
> <project><echo>hello from stdin</echo></project>
> EOF
Buildfile: /dev/stdin
     [echo] hello from stdin

BUILD SUCCESSFUL
Total time: 0 seconds