Optimize task storeGitComInf lifecycle detection

by having Gradle monitor .git directory changes
to speed up subsequent builds with min changes.

build.gradle

@@ -150,7 +150,7 @@ jar {
 shadowJar.zip64 = true // saw build error: Execution failed for task ':shadowJar'. shadow.org.apache.tools.zip.Zip64RequiredException: archive contains more than 65535 entries.
 
 // prepare yacyBuildProperties.java from template (needed after commits or new versions)
-// read values from property file generated by GitComInf tool
+// read values from property file generated by storeGitComInf tool
 import org.apache.tools.ant.filters.ReplaceTokens
 task prepYaCyProperties (type: Copy) {
 
@@ -162,7 +162,7 @@ task prepYaCyProperties (type: Copy) {
             project.ext.filterTokens.putAll(props)
         }
     } else { // on missing properties file use generic data
-        logger.error("prepYaCyProperties: file " + propfile + " is missing, you should re-run runGitComInf")
+        logger.error("prepYaCyProperties: file " + propfile + " is missing, you should re-run storeGitComInf")
         Properties props = new Properties()
         String Dstr = new Date().format("yyyyMMDD")
         String Tstr = new Date().format("yyyyMMDD-HHmmss")
@@ -177,7 +177,7 @@ task prepYaCyProperties (type: Copy) {
     include('yacyBuildProperties.java.template')
     rename 'yacyBuildProperties.java.template', 'yacyBuildProperties.java'
     filter(org.apache.tools.ant.filters.ReplaceTokens, tokens: project.ext.filterTokens)
-    filter(ReplaceTokens, tokens: [REPL_VERSION: version, REPL_PKGMANAGER:"false", REPL_RESTARTCMD: "/etc/init.d/yacy restart"]) // gradle.project.version + some defaults from ant
+    filter(ReplaceTokens, tokens: [REPL_VERSION: project.version, REPL_PKGMANAGER:"false", REPL_RESTARTCMD: "/etc/init.d/yacy restart"]) // gradle.project.version + some defaults from ant
     into (fdirname)
     
 }
@@ -269,7 +269,7 @@ distributions {
         // String rNr = project.ext.filterTokens.get('REPL_REVISION_NR')
         // String branch = project.ext.filterTokens.get('branch')
         //
-        // distributionBaseName = 'yacy' + branch + '_v' + version + '_' + Dst + '_' + rNr
+        // distributionBaseName = 'yacy' + branch + '_v' + project.version + '_' + Dst + '_' + rNr
         
         contents { // fyi: content completed by copyFilesToDistDir
             from "${buildDir}/RELEASE/MAIN"
@@ -340,7 +340,7 @@ task packageDistTar (type : Tar, dependsOn : ['copyDependenciesForDistribution',
     String Dst = project.ext.filterTokens.get('REPL_DATE')
     String rNr = project.ext.filterTokens.get('REPL_REVISION_NR')
     String branch = project.ext.filterTokens.get('branch')    
-    String destName = 'yacy' + branch + '_v' + version + '_' + Dst + '_' + rNr + '.tar.gz' // ! Gradle would use ext .tgz (archiveExtension.get()) 
+    String destName = 'yacy' + branch + '_v' + project.version + '_' + Dst + '_' + rNr + '.tar.gz' // ! Gradle would use ext .tgz (archiveExtension.get()) 
 
     archiveFileName = destName
     destinationDirectory = layout.buildDirectory.dir('distributions/legacyDistFiles')
@@ -365,7 +365,7 @@ task packageDist (dependsOn : ['packageDistZip','packageDistTar'],group:'distrib
 // configure Javadoc task
 tasks.withType (Javadoc) {
     destinationDir  project.file("javadoc")
-    title = "YaCy " + version + " API Documentation"
+    title = "YaCy " + project.version + " API Documentation"
     failOnError = false
     options.addStringOption("encoding","UTF-8" ) // or any reason to keep the old "iso-8859-1" ?
     classpath = configurations.compileClasspath
@@ -410,7 +410,7 @@ task prepNsis (type: Copy, dependsOn: ['prepYaCyProperties']) {
     into "${buildDir}/RELEASE/WINDOWS"
 
     filter(org.apache.tools.ant.filters.ReplaceTokens, tokens: project.ext.filterTokens)
-    filter(ReplaceTokens, tokens: [REPL_VERSION: version])
+    filter(ReplaceTokens, tokens: [REPL_VERSION: project.version])
 
     copy {
         from projectDir
@@ -427,7 +427,14 @@ task distWinInstaller (dependsOn:['copyFilesToDistDir','copyDependenciesForDistr
 
 // runs the support tool which creates gitbuildnumber.properties from info of local git repository
 task storeGitComInf(type: JavaExec) {
+    outputs.file "gitbuildnumber.properties"
     mustRunAfter(build)
+    if (file(".git").exists()) { // check if this is a git repos
+        inputs.files ( fileTree(".git") {
+            include "refs/**/*"  // these two should work and change after commit
+            include "index"
+        } )
+    }
     classpath = files('libbuild/GitComInf-1.0-all.jar')
     args = [project.projectDir.getPath(), project.projectDir.getPath() + "/gitbuildnumber.properties"]
     mainClass = 'GitComInf'