Auto-enable git wire protocol v2 in jgit

By JGit's default, git wire protocol version 2 is disabled. The attempt
to activate it per default in JGit wasn't approved yet: [1],[2]. Given,
that git wire protocol version 2 on server side is considered to be now
very stable, activate it per default in init site program.

Update JGit module to include the following change:

23389a632 Add constants for parsing git wire protocol version

[1] https://bugs.eclipse.org/bugs/show_bug.cgi?id=563145
[2] https://git.eclipse.org/r/c/jgit/jgit/+/163216

Change-Id: I15da7c5e889bc222da08d473a4c41e349a2ee6a6

java/com/google/gerrit/pgm/init/InitJGitConfig.java

@@ -25,6 +25,7 @@ import java.io.IOException;
 import org.eclipse.jgit.errors.ConfigInvalidException;
 import org.eclipse.jgit.lib.ConfigConstants;
 import org.eclipse.jgit.storage.file.FileBasedConfig;
+import org.eclipse.jgit.transport.TransferConfig;
 import org.eclipse.jgit.util.FS;
 
 /** Initialize the JGit configuration. */
@@ -62,6 +63,36 @@ class InitJGitConfig implements InitStep {
                 + "Disable this behavior to avoid the additional load it creates: "
                 + "gc should be configured in gc config section or run as a separate process.");
       }
+
+      if (!jgitConfig
+          .getNames(ConfigConstants.CONFIG_PROTOCOL_SECTION)
+          .contains(ConfigConstants.CONFIG_KEY_VERSION)) {
+        jgitConfig.setString(
+            ConfigConstants.CONFIG_PROTOCOL_SECTION,
+            null,
+            ConfigConstants.CONFIG_KEY_VERSION,
+            TransferConfig.ProtocolVersion.V2.version());
+        jgitConfig.save();
+        ui.error(
+            String.format(
+                "Auto-configured \"%s.%s = %s\" to activate git wire protocol version 2.",
+                ConfigConstants.CONFIG_PROTOCOL_SECTION,
+                ConfigConstants.CONFIG_KEY_VERSION,
+                TransferConfig.ProtocolVersion.V2.version()));
+      } else {
+        String version =
+            jgitConfig.getString(
+                ConfigConstants.CONFIG_PROTOCOL_SECTION, null, ConfigConstants.CONFIG_KEY_VERSION);
+        if (!TransferConfig.ProtocolVersion.V2.version().equals(version)) {
+          ui.error(
+              String.format(
+                  "HINT: JGit option \"%s.%s = %s\". It's recommended to activate git\n"
+                      + "wire protocol version 2 to improve git fetch performance.",
+                  ConfigConstants.CONFIG_PROTOCOL_SECTION,
+                  ConfigConstants.CONFIG_KEY_VERSION,
+                  version));
+        }
+      }
     } catch (IOException e) {
       throw die(String.format("Handling JGit configuration %s failed", sitePaths.jgit_config), e);
     } catch (ConfigInvalidException e) {