Flatten first directory of a FileTree in Gradle - groovy

Question

I'm writing a task to extract a tarball into a directory. I don't control this tarball's contents.
The tarball contains a single directory which contains all the files I actually care about. I want to pull everything out of that directory and copy that into my destination.
Example:
/root/subdir
/root/subdir/file1
/root/file2
Desired:
/subdir
/subdir/file1
/file2
Here's what I tried so far, but this seems like a really goofy way of doing it:
copy {
eachFile {
def segments = it.getRelativePath().getSegments() as List
it.setPath(segments.tail().join("/"))
return it
}
from tarTree(resources.gzip('mytarfile.tar.gz'))
into destinationDir
}
For each file, I get the elements of its path, remove the first, join that with /, then set that as the file's path. And this works...sort of. The problem is that this creates the following structure as a result:
/root/subdir
/root/subdir/file1
/root/file2
/subdir
/subdir/file1
/file2
I'm fine with just removing the root directory myself as a final action of the task, but I feel like there should be a much simpler way of doing this.

Answer 1

AFAIK, the only way is to unpack the zip, tar, tgz file :(
There is an open issue here
Please go vote for it!
Until then, the solution isn't very pretty, but not that hard either. In the example below, I am assuming that you want to remove the 'apache-tomcat-XYZ' root-level directory from a 'tomcat' configuration that only includes the apache-tomcat zip file.
def unpackDir = "$buildDir/tmp/apache.tomcat.unpack"
task unpack(type: Copy) {
from configurations.tomcat.collect {
zipTree(it).matching {
// these would be global items I might want to exclude
exclude '**/EMPTY.txt'
exclude '**/examples/**', '**/work/**'
}
}
into unpackDir
}
def mainFiles = copySpec {
from {
// use of a closure here defers evaluation until execution time
// It might not be clear, but this next line "moves down"
// one directory and makes everything work
"${unpackDir}/apache-tomcat-7.0.59"
}
// these excludes are only made up for an example
// you would only use/need these here if you were going to have
// multiple such copySpec's. Otherwise, define everything in the
// global unpack above.
exclude '**/webapps/**'
exclude '**/lib/**'
}
task createBetterPackage(type: Zip) {
baseName 'apache-tomcat'
with mainFiles
}
createBetterPackage.dependsOn(unpack)

Answer 2

Using groovy's syntax, we can use a regex to eliminate the first path segment:
task myCopyTask(type: Copy) {
eachFile {
path -= ~/^.+?\//
}
from tarTree(resources.gzip('mytarfile.tar.gz'))
into destinationDir
includeEmptyDirs = false // ignore empty directories
}