Git should ignore user config (#3883)

Ignore gitconfig located in the user's home directory when creating Git instance.

For example, I setup git to automatically sign commits. And all git related tests are failing because of that:

```
[info] - should return last X commits *** FAILED ***
[info]   org.eclipse.jgit.api.errors.ServiceUnavailableException: Signing service is not available
[info]   at org.eclipse.jgit.api.CommitCommand.sign(CommitCommand.java:328)
[info]   at org.eclipse.jgit.api.CommitCommand.call(CommitCommand.java:283)
[info]   at org.enso.languageserver.vcsmanager.GitSpec$InitialRepoSetup.setup(GitSpec.scala:360)
[info]   at org.enso.languageserver.vcsmanager.GitSpec$InitialRepoSetup.setup$(GitSpec.scala:348)
[info]   at org.enso.languageserver.vcsmanager.GitSpec$$anon$16.setup(GitSpec.scala:275)
[info]   at org.enso.languageserver.vcsmanager.GitSpec$InitialRepoSetup.$init$(GitSpec.scala:346)
[info]   at org.enso.languageserver.vcsmanager.GitSpec$$anon$16.<init>(GitSpec.scala:275)
[info]   at org.enso.languageserver.vcsmanager.GitSpec.$anonfun$new$35(GitSpec.scala:275)
[info]   at org.scalatest.OutcomeOf.outcomeOf(OutcomeOf.scala:85)
[info]   at org.scalatest.OutcomeOf.outcomeOf$(OutcomeOf.scala:83)
[info]   ...
```

engine/language-server/src/main/scala/org/enso/languageserver/boot/MainModule.scala

@@ -105,7 +105,7 @@ class MainModule(serverConfig: LanguageServerConfig, logLevel: LogLevel) {
   val fileSystem: FileSystem = new FileSystem
   log.trace("Created file system [{}].", fileSystem)
 
-  val git = Git()
+  val git = Git.withEmptyUserConfig()
   log.trace("Created git [{}].", git)
 
   implicit val versionCalculator: ContentBasedVersioning =

engine/language-server/src/main/scala/org/enso/languageserver/vcsmanager/EmptyUserConfigReader.scala

@@ -0,0 +1,65 @@
+package org.enso.languageserver.vcsmanager
+
+import org.apache.commons.io.FileUtils
+import org.eclipse.jgit.lib.Config
+import org.eclipse.jgit.storage.file.FileBasedConfig
+import org.eclipse.jgit.util.{FS, SystemReader}
+
+import java.io.File
+import java.nio.file.Files
+
+/** Config reader that ignores gitconfig file in user's home directory.
+  */
+final class EmptyUserConfigReader extends SystemReader {
+
+  import EmptyUserConfigReader._
+
+  val proxy: SystemReader = SystemReader.getInstance()
+
+  /** @inheritdoc */
+  override def getHostname: String =
+    proxy.getHostname
+
+  /** @inheritdoc */
+  override def getenv(variable: String): String =
+    proxy.getenv(variable)
+
+  /** @inheritdoc */
+  override def getProperty(key: String): String =
+    proxy.getProperty(key)
+
+  /** @inheritdoc */
+  override def openUserConfig(parent: Config, fs: FS): FileBasedConfig =
+    new EmptyConfig(parent, fs)
+
+  /** @inheritdoc */
+  override def openSystemConfig(parent: Config, fs: FS): FileBasedConfig =
+    proxy.openSystemConfig(parent, fs)
+
+  /** @inheritdoc */
+  override def openJGitConfig(parent: Config, fs: FS): FileBasedConfig =
+    proxy.openJGitConfig(parent, fs)
+
+  /** @inheritdoc */
+  override def getCurrentTime: Long =
+    proxy.getCurrentTime
+
+  /** @inheritdoc */
+  override def getTimezone(when: Long): Int =
+    proxy.getTimezone(when)
+}
+
+object EmptyUserConfigReader {
+
+  private val gitconfig: File =
+    Files.createTempFile("gitconfig", null).toFile
+
+  sys.addShutdownHook(FileUtils.deleteQuietly(gitconfig))
+
+  final private class EmptyConfig(parent: Config, fs: FS)
+      extends FileBasedConfig(parent, gitconfig, fs) {
+    override def load(): Unit  = ()
+    override def save(): Unit  = ()
+    override def clear(): Unit = ()
+  }
+}

engine/language-server/src/main/scala/org/enso/languageserver/vcsmanager/Git.scala

@@ -15,6 +15,7 @@ import org.eclipse.jgit.errors.{
 import org.eclipse.jgit.lib.{ObjectId, Repository}
 import org.eclipse.jgit.storage.file.FileRepositoryBuilder
 import org.eclipse.jgit.revwalk.{RevCommit, RevWalk}
+import org.eclipse.jgit.util.SystemReader
 import org.enso.languageserver.vcsmanager.Git.{
   AuthorEmail,
   AuthorName,
@@ -31,7 +32,7 @@ import java.time.Instant
 private class Git extends VcsApi[BlockingIO] {
 
   private def repository(path: Path): Repository = {
-    val builder = new FileRepositoryBuilder();
+    val builder = new FileRepositoryBuilder()
     builder
       .setGitDir(path.resolve(Git.DefaultGitRepoDir).toFile)
       .setMustExist(true)
@@ -171,7 +172,7 @@ private class Git extends VcsApi[BlockingIO] {
       val logCmd = jgit.log()
       limit
         .filter(_ > 0)
-        .map(logCmd.setMaxCount(_))
+        .map(logCmd.setMaxCount)
         .getOrElse(logCmd)
         .call()
         .asScala
@@ -197,7 +198,11 @@ object Git {
 
   private class RepoExists extends Exception
 
-  /** Returns a Git implementation of VcsApi
+  /** Returns a Git implementation of VcsApi that ignores gitconfig file in
+    * user's home directory.
     */
-  def apply(): VcsApi[BlockingIO] = new Git()
+  def withEmptyUserConfig(): VcsApi[BlockingIO] = {
+    SystemReader.setInstance(new EmptyUserConfigReader)
+    new Git()
+  }
 }

engine/language-server/src/main/scala/org/enso/languageserver/vcsmanager/VcsManager.scala

@@ -37,7 +37,7 @@ class VcsManager(
       .absolve
 
   private def toVcsError: FileSystemFailure => VcsFailure = {
-    case ex: FileSystemFailure => ProjectNotFound(ex.toString)
+    ex: FileSystemFailure => ProjectNotFound(ex.toString)
   }
 
   private def resolvePath(path: Path): IO[VcsFailure, File] =

engine/language-server/src/test/scala/org/enso/languageserver/vcsmanager/GitSpec.scala

@@ -312,7 +312,7 @@ class GitSpec extends AnyWordSpecLike with Matchers with Effects {
         .build()
     }
 
-    val vcs = Git()
+    val vcs = Git.withEmptyUserConfig()
 
     def listCommits(repoDir: Path): List[RevCommit] = {
       listCommits(testRepo(repoDir))

engine/language-server/src/test/scala/org/enso/languageserver/websocket/json/BaseServerTest.scala

@@ -170,7 +170,7 @@ class BaseServerTest
     val vcsManager = system.actorOf(
       VcsManager.props(
         config.vcsManager,
-        Git(),
+        Git.withEmptyUserConfig(),
         contentRootManagerWrapper,
         zioExec
       ),