Supported include keys in gitblit.properties

This allows you to build a hierarchy of properties files or for a properties file
to include default settings.

src/main/java/com/gitblit/FileSettings.java

@@ -18,10 +18,13 @@ package com.gitblit;
 import java.io.File;
 import java.io.FileInputStream;
 import java.io.FileNotFoundException;
+import java.io.IOException;
+import java.util.List;
 import java.util.Map;
 import java.util.Properties;
 
 import com.gitblit.utils.FileUtils;
+import com.gitblit.utils.StringUtils;
 
 /**
  * Dynamically loads and reloads a properties file by keeping track of the last
@@ -81,6 +84,9 @@ public class FileSettings extends IStoredSettings {
 				is = new FileInputStream(propertiesFile);
 				props.load(is);
 
+				// ticket-110
+				props = readIncludes(props);
+
 				// load properties after we have successfully read file
 				properties.clear();
 				properties.putAll(props);
@@ -103,6 +109,55 @@ public class FileSettings extends IStoredSettings {
 		return properties;
 	}
 
+	/**
+	 * Recursively read "include" properties files.
+	 *
+	 * @param properties
+	 * @return
+	 * @throws IOException
+	 */
+	private Properties readIncludes(Properties properties) throws IOException {
+
+		Properties baseProperties = new Properties();
+
+		String include = (String) properties.remove("include");
+		if (!StringUtils.isEmpty(include)) {
+
+			// allow for multiples
+			List<String> names = StringUtils.getStringsFromValue(include, " ");
+			for (String name : names) {
+
+				// try co-located
+				File file = new File(propertiesFile.getParentFile(), name.trim());
+				if (!file.exists()) {
+					// try absolute path
+					file = new File(name.trim());
+				}
+
+				if (file.exists()) {
+					// load properties
+					try (FileInputStream iis = new FileInputStream(file)) {
+						baseProperties.load(iis);
+					}
+
+					// read nested includes
+					baseProperties = readIncludes(baseProperties);
+
+				}
+
+			}
+
+		}
+
+		// includes are "default" properties, they must be set first and the
+		// props which specified the "includes" must override
+		Properties merged = new Properties();
+		merged.putAll(baseProperties);
+		merged.putAll(properties);
+
+		return merged;
+	}
+
 	@Override
 	public boolean saveSettings() {
 		String content = FileUtils.readContent(propertiesFile, "\n");