Store filesystem timestamp resolution in extra jgit config

This avoids polluting hand-crafted user level config with
auto-configured options which might disturb in environments where
the user level config is replicated between different machines.

Add a jgit config as parent of the system level config. Persist
measured timestamp resolutions always in this jgit config and read it
via the user global config. This has the effect that auto-configured
timestamp resolution will be used by default and can be overridden in
either the system level or user level config.

Store the jgit config under the XDG_CONFIG_HOME directory following the
XDG base directory specification [1] in order to ensure that we have
write permissions to persist the file. This has the effect that each OS
user will use its jgit config since they typically use different
XDG_CONFIG_HOME directories.

If the environment variable XDG_CONFIG_HOME is defined the jgit config
file is located at $XDG_CONFIG_HOME/jgit/config otherwise the default is
~/.config/jgit/config.

If you want to avoid redundant measurement for different OS users
manually copy the values measured and auto-configured for one OS user to
the system level git config.

[1] https://wiki.archlinux.org/index.php/XDG_Base_Directory

Bug: 551850
Change-Id: I0022bd40ae62f82e5b964c2ea25822eb55d94687
Signed-off-by: Matthias Sohn <matthias.sohn@sap.com>

4 files changed, 104 insertions, 15 deletions

diff --git a/org.eclipse.jgit/src/org/eclipse/jgit/internal/JGitText.java b/org.eclipse.jgit/src/org/eclipse/jgit/internal/JGitText.java
index 6a7d22df9d..61b145657d 100644
--- a/org.eclipse.jgit/src/org/eclipse/jgit/internal/JGitText.java
+++ b/org.eclipse.jgit/src/org/eclipse/jgit/internal/JGitText.java
@@ -262,8 +262,10 @@ public class JGitText extends TranslationBundle {
 	/***/ public String countingObjects;
 	/***/ public String createBranchFailedUnknownReason;
 	/***/ public String createBranchUnexpectedResult;
+	/***/ public String createJGitConfigFailed;
 	/***/ public String createNewFileFailed;
 	/***/ public String createRequiresZeroOldId;
+	/***/ public String createXDGConfigHomeFailed;
 	/***/ public String credentialPassword;
 	/***/ public String credentialPassphrase;
 	/***/ public String credentialUsername;
diff --git a/org.eclipse.jgit/src/org/eclipse/jgit/lib/Constants.java b/org.eclipse.jgit/src/org/eclipse/jgit/lib/Constants.java
index a084c82871..9274fc6777 100644
--- a/org.eclipse.jgit/src/org/eclipse/jgit/lib/Constants.java
+++ b/org.eclipse.jgit/src/org/eclipse/jgit/lib/Constants.java
@@ -343,6 +343,15 @@ public final class Constants {
 	public static final String GIT_CONFIG_NOSYSTEM_KEY = "GIT_CONFIG_NOSYSTEM";
 
 	/**
+	 * The key of the XDG_CONFIG_HOME directory defined in the XDG base
+	 * directory specification, see
+	 * {@link "https://wiki.archlinux.org/index.php/XDG_Base_Directory"}
+	 *
+	 * @since 5.5.2
+	 */
+	public static final String XDG_CONFIG_HOME = "XDG_CONFIG_HOME";
+
+	/**
 	 * The environment variable that limits how close to the root of the file
 	 * systems JGit will traverse when looking for a repository root.
 	 */
diff --git a/org.eclipse.jgit/src/org/eclipse/jgit/util/FS.java b/org.eclipse.jgit/src/org/eclipse/jgit/util/FS.java
index 29519298c4..b3d01d3b48 100644
--- a/org.eclipse.jgit/src/org/eclipse/jgit/util/FS.java
+++ b/org.eclipse.jgit/src/org/eclipse/jgit/util/FS.java
@@ -545,9 +545,9 @@ public abstract class FS {
 
 		private static void saveToConfig(FileStore s,
 				FileStoreAttributes c) {
-			StoredConfig userConfig;
+			StoredConfig jgitConfig;
 			try {
-				userConfig = SystemReader.getInstance().getUserConfig();
+				jgitConfig = SystemReader.getInstance().getJGitConfig();
 			} catch (IOException | ConfigInvalidException e) {
 				LOG.error(JGitText.get().saveFileStoreAttributesFailed, e);
 				return;
@@ -568,20 +568,19 @@ public abstract class FS {
 			String key = getConfigKey(s);
 			while (!succeeded && retries < max_retries) {
 				try {
-					userConfig.load();
-					userConfig.setString(
+					jgitConfig.setString(
 							ConfigConstants.CONFIG_FILESYSTEM_SECTION, key,
 							ConfigConstants.CONFIG_KEY_TIMESTAMP_RESOLUTION,
 							String.format("%d %s", //$NON-NLS-1$
 									Long.valueOf(resolutionValue),
 									resolutionUnit.name().toLowerCase()));
-					userConfig.setString(
+					jgitConfig.setString(
 							ConfigConstants.CONFIG_FILESYSTEM_SECTION, key,
 							ConfigConstants.CONFIG_KEY_MIN_RACY_THRESHOLD,
 							String.format("%d %s", //$NON-NLS-1$
 									Long.valueOf(minRacyThresholdValue),
 									minRacyThresholdUnit.name().toLowerCase()));
-					userConfig.save();
+					jgitConfig.save();
 					succeeded = true;
 				} catch (LockFailedException e) {
 					// race with another thread, wait a bit and try again
@@ -590,11 +589,11 @@ public abstract class FS {
 						if (retries < max_retries) {
 							Thread.sleep(100);
 							LOG.debug("locking {} failed, retries {}/{}", //$NON-NLS-1$
-									userConfig, Integer.valueOf(retries),
+									jgitConfig, Integer.valueOf(retries),
 									Integer.valueOf(max_retries));
 						} else {
 							LOG.warn(MessageFormat.format(
-									JGitText.get().lockFailedRetry, userConfig,
+									JGitText.get().lockFailedRetry, jgitConfig,
 									Integer.valueOf(retries)));
 						}
 					} catch (InterruptedException e1) {
@@ -603,12 +602,7 @@ public abstract class FS {
 					}
 				} catch (IOException e) {
 					LOG.error(MessageFormat.format(
-							JGitText.get().cannotSaveConfig, userConfig), e);
-					break;
-				} catch (ConfigInvalidException e) {
-					LOG.error(MessageFormat.format(
-							JGitText.get().repositoryConfigFileInvalid,
-							userConfig, e.getMessage()));
+							JGitText.get().cannotSaveConfig, jgitConfig), e);
 					break;
 				}
 			}
diff --git a/org.eclipse.jgit/src/org/eclipse/jgit/util/SystemReader.java b/org.eclipse.jgit/src/org/eclipse/jgit/util/SystemReader.java
index a2253bc118..59184ffda2 100644
--- a/org.eclipse.jgit/src/org/eclipse/jgit/util/SystemReader.java
+++ b/org.eclipse.jgit/src/org/eclipse/jgit/util/SystemReader.java
@@ -50,6 +50,10 @@ import java.io.File;
 import java.io.IOException;
 import java.net.InetAddress;
 import java.net.UnknownHostException;
+import java.nio.file.Files;
+import java.nio.file.InvalidPathException;
+import java.nio.file.Path;
+import java.nio.file.Paths;
 import java.security.AccessController;
 import java.security.PrivilegedAction;
 import java.text.DateFormat;
@@ -60,6 +64,7 @@ import java.util.concurrent.atomic.AtomicReference;
 
 import org.eclipse.jgit.errors.ConfigInvalidException;
 import org.eclipse.jgit.errors.CorruptObjectException;
+import org.eclipse.jgit.internal.JGitText;
 import org.eclipse.jgit.lib.Config;
 import org.eclipse.jgit.lib.Constants;
 import org.eclipse.jgit.lib.ObjectChecker;
@@ -137,6 +142,42 @@ public abstract class SystemReader {
 					fs);
 		}
 
+		private Path getXDGConfigHome(FS fs) {
+			String configHomePath = getenv(Constants.XDG_CONFIG_HOME);
+			if (StringUtils.isEmptyOrNull(configHomePath)) {
+				configHomePath = new File(fs.userHome(), ".config") //$NON-NLS-1$
+						.getAbsolutePath();
+			}
+			try {
+				Path xdgHomePath = Paths.get(configHomePath);
+				Files.createDirectories(xdgHomePath);
+				return xdgHomePath;
+			} catch (IOException | InvalidPathException e) {
+				LOG.error(JGitText.get().createXDGConfigHomeFailed,
+						configHomePath, e);
+			}
+			return null;
+		}
+
+		@Override
+		public FileBasedConfig openJGitConfig(Config parent, FS fs) {
+			Path xdgPath = getXDGConfigHome(fs);
+			if (xdgPath != null) {
+				Path configPath = null;
+				try {
+					configPath = xdgPath.resolve("jgit"); //$NON-NLS-1$
+					Files.createDirectories(configPath);
+					configPath = configPath.resolve(Constants.CONFIG);
+					return new FileBasedConfig(parent, configPath.toFile(), fs);
+				} catch (IOException e) {
+					LOG.error(JGitText.get().createJGitConfigFailed, configPath,
+							e);
+				}
+			}
+			return new FileBasedConfig(parent,
+					new File(fs.userHome(), ".jgitconfig"), fs); //$NON-NLS-1$
+		}
+
 		@Override
 		public String getHostname() {
 			if (hostname == null) {
@@ -198,6 +239,8 @@ public abstract class SystemReader {
 
 	private AtomicReference<FileBasedConfig> userConfig = new AtomicReference<>();
 
+	private AtomicReference<FileBasedConfig> jgitConfig = new AtomicReference<>();
+
 	private void init() {
 		// Creating ObjectChecker must be deferred. Unit tests change
 		// behavior of is{Windows,MacOS} in constructor of subclass.
@@ -275,6 +318,22 @@ public abstract class SystemReader {
 	public abstract FileBasedConfig openSystemConfig(Config parent, FS fs);
 
 	/**
+	 * Open the jgit configuration located at $XDG_CONFIG_HOME/jgit/config. Use
+	 * {@link #getJGitConfig()} to get the current jgit configuration in the
+	 * user home since it manages automatic reloading when the jgit config file
+	 * was modified and avoids unnecessary reloads.
+	 *
+	 * @param parent
+	 *            a config with values not found directly in the returned config
+	 * @param fs
+	 *            the file system abstraction which will be necessary to perform
+	 *            certain file system operations.
+	 * @return the jgit configuration located at $XDG_CONFIG_HOME/jgit/config
+	 * @since 5.5.2
+	 */
+	public abstract FileBasedConfig openJGitConfig(Config parent, FS fs);
+
+	/**
 	 * Get the git configuration found in the user home. The configuration will
 	 * be reloaded automatically if the configuration file was modified. Also
 	 * reloads the system config if the system config file was modified. If the
@@ -302,6 +361,31 @@ public abstract class SystemReader {
 	}
 
 	/**
+	 * Get the jgit configuration located at $XDG_CONFIG_HOME/jgit/config. The
+	 * configuration will be reloaded automatically if the configuration file
+	 * was modified. If the configuration file wasn't modified returns the
+	 * cached configuration.
+	 *
+	 * @return the jgit configuration located at $XDG_CONFIG_HOME/jgit/config
+	 * @throws ConfigInvalidException
+	 *             if configuration is invalid
+	 * @throws IOException
+	 *             if something went wrong when reading files
+	 * @since 5.5.2
+	 */
+	public StoredConfig getJGitConfig()
+			throws ConfigInvalidException, IOException {
+		FileBasedConfig c = jgitConfig.get();
+		if (c == null) {
+			jgitConfig.compareAndSet(null,
+					openJGitConfig(null, FS.DETECTED));
+			c = jgitConfig.get();
+		}
+		updateAll(c);
+		return c;
+	}
+
+	/**
 	 * Get the gitconfig configuration found in the system-wide "etc" directory.
 	 * The configuration will be reloaded automatically if the configuration
 	 * file was modified otherwise returns the cached system level config.
@@ -319,7 +403,7 @@ public abstract class SystemReader {
 		FileBasedConfig c = systemConfig.get();
 		if (c == null) {
 			systemConfig.compareAndSet(null,
-					openSystemConfig(null, FS.DETECTED));
+					openSystemConfig(getJGitConfig(), FS.DETECTED));
 			c = systemConfig.get();
 		}
 		updateAll(c);