Gradle task to write hg revision to file - version-control

Question

Is there a simple way to write to file the mercurial version (or similar external command) in a gradle task:
I'm not yet groovy/gradle conversant, but my current effort looks like this:
task versionInfo(type:Exec){
commandLine 'hg id -i -b -t'
ext.versionfile = new File('bin/$baseName-buildinfo.properties')
doLast {
versionfile.text = 'build.revision=' + standardOutput.toString()
}
}

Answer 1

There are two issues with this build script:
the command line needs to be split; gradle's trying to execute a binary named hg id -i -b t instead of hg with arguments id, -i, -b and t
The standard output needs to be captured; you can make it a ByteOutputStream to be read later
Try this:
task versionInfo(type:Exec){
commandLine 'hg id -i -b -t'.split()
ext.versionfile = new File('bin/$baseName-buildinfo.properties')
standardOutput = new ByteArrayOutputStream()
doLast {
versionfile.text = 'build.revision=' + standardOutput.toString()
}
}

Answer 2

Here I have a little bit different approach, which uses javahg to get revision. And add task "writeRevisionToFile"
I wrote brief post on my blog Gradle - Get Hg Mercurial revision.
buildscript {
repositories {
mavenCentral()
}
dependencies {
classpath 'com.aragost.javahg:javahg:0.4'
}
}
task writeRevisionToFile << {
new File(projectDir, "file-with-revision.txt").text = scmRevision
}
import com.aragost.javahg.Changeset
import com.aragost.javahg.Repository
import com.aragost.javahg.commands.ParentsCommand
String getHgRevision() {
def repo = Repository.open(projectDir)
def parentsCommand = new ParentsCommand(repo)
List<Changeset> changesets = parentsCommand.execute()
if (changesets == null || changesets.size() != 1) {
def message = "Exactly one was parent expected. " + changesets
throw new Exception(message)
}
return changesets[0].node
}
ext {
scmRevision = getHgRevision()
}