Improve up-to-date detection

build.gradle

@@ -12,7 +12,7 @@ plugins {
 }
 
 group = 'net.minecrell'
-version = '0.6-SNAPSHOT'
+version = '0.6'
 description = 'A Gradle plugin to manage patches for Git repositories'
 
 sourceCompatibility = 1.6

src/main/groovy/net/minecrell/gitpatcher/Git.groovy

@@ -34,9 +34,21 @@ class Git {
         assert repo.exists()
     }
 
+    String getStatus() {
+        return run('status', ['-z']) as String
+    }
+
+    String getRef() {
+        return show_ref('-s', 'HEAD') as String
+    }
+
+    Command run(String name, Object input) {
+        return new Command(['git', name.replace('_' as char, '-' as char), *input].execute(null as String[], repo))
+    }
+
     @Override
     Command invokeMethod(String name, Object input) {
-        return new Command(['git', name.replace('_' as char, '-' as char), *input].execute(null as String[], repo))
+        return run(name, input)
     }
 
     static class Command {

src/main/groovy/net/minecrell/gitpatcher/task/GitTask.groovy

@@ -27,8 +27,4 @@ abstract class GitTask extends DefaultTask {
 
     File repo
 
-    protected File getIndexFile() {
-        return new File(new File(repo, '.git'), 'index')
-    }
-
 }

src/main/groovy/net/minecrell/gitpatcher/task/patch/ApplyPatchesTask.groovy

@@ -42,8 +42,19 @@ class ApplyPatchesTask extends PatchTask {
     }
 
     @Override @OutputFile
-    File getIndexFile() {
-        return super.getIndexFile()
+    File getRefCache() {
+        return super.getRefCache()
+    }
+
+    {
+        outputs.upToDateWhen {
+            if (!repo.directory) {
+                return false
+            }
+
+            def git = new Git(repo)
+            return git.status.empty && cachedRef == git.ref
+        }
     }
 
     @TaskAction
@@ -76,6 +87,7 @@ class ApplyPatchesTask extends PatchTask {
             logger.lifecycle 'Successfully applied patches from {} to {}', patchDir, repo
         }
 
+        refCache.text = git.ref
     }
 
 }

src/main/groovy/net/minecrell/gitpatcher/task/patch/MakePatchesTask.groovy

@@ -39,15 +39,26 @@ class MakePatchesTask extends PatchTask {
     }
 
     @Override @InputFile
-    File getIndexFile() {
-        return super.getIndexFile()
+    File getRefCache() {
+        return super.getRefCache()
     }
 
     @Override @OutputDirectory
     File getPatchDir() {
         return super.getPatchDir()
     }
 
+    {
+        outputs.upToDateWhen {
+            if (!repo.directory) {
+                return false
+            }
+
+            def git = new Git(repo)
+            return cachedRef == git.ref
+        }
+    }
+
     @TaskAction
     void makePatches() {
         if (patchDir.isDirectory()) {

src/main/groovy/net/minecrell/gitpatcher/task/patch/PatchTask.groovy

@@ -37,4 +37,16 @@ abstract class PatchTask extends SubmoduleTask {
         return new File(root, submodule)
     }
 
+    File getGitDir() {
+        return new File(repo, '.git')
+    }
+
+    File getRefCache() {
+        return new File(gitDir, '.gitpatcher_ref')
+    }
+
+    String getCachedRef() {
+        return refCache.file ? refCache.text : null
+    }
+
 }