When opening a repo in a dir that is not a bare repo then an exception is thrown

src/main/java/net/kemitix/gitdb/GitDB.java

@@ -53,14 +53,21 @@ public interface GitDB {
      *
      * @param dbDir the path to open as a local repo
      * @return a GitDB instance for the local gitdb
-     * @throws IOException if there {@code dbDir} is a file, the directory does not exist or is not a repo
+     * @throws IOException if there {@code dbDir} is a file, the directory does not exist or is not a bare repo
      */
     static GitDBLocal openLocal(final Path dbDir) throws IOException {
         try {
             final Git git = Git.open(dbDir.toFile());
+            verifyIsBareRepo(dbDir, git);
             return new GitDBLocal(git);
         } catch (RepositoryNotFoundException e) {
             throw new GitDBRepoNotFoundException(dbDir, e);
         }
     }
+
+    static void verifyIsBareRepo(final Path dbDir, final Git git) {
+        if (!git.getRepository().isBare()) {
+            throw new InvalidRepositoryException("Not a bare repo", dbDir);
+        }
+    }
 }

src/main/java/net/kemitix/gitdb/InvalidRepositoryException.java

@@ -0,0 +1,21 @@
+package net.kemitix.gitdb;
+
+import java.nio.file.Path;
+
+/**
+ * Runtime exception thrown when attempting to open a repository that it not a GitDB repo.
+ *
+ * @author Paul Campbell (pcampbell@kemitix.net)
+ */
+public class InvalidRepositoryException extends RuntimeException {
+
+    /**
+     * Constructor.
+     *
+     * @param message the reason the repo is invalid
+     * @param path the location of the repo
+     */
+    public InvalidRepositoryException(final String message, final Path path) {
+        super(String.format("Invalid GitDB repo: %s [%s]", message, path));
+    }
+}

src/test/java/net/kemitix/gitdb/GitDBTest.java

@@ -1,6 +1,7 @@
 package net.kemitix.gitdb;
 
 import org.assertj.core.api.WithAssertions;
+import org.eclipse.jgit.api.Git;
 import org.eclipse.jgit.api.InitCommand;
 import org.eclipse.jgit.api.errors.GitAPIException;
 import org.junit.jupiter.api.Test;
@@ -149,6 +150,25 @@ class GitDBTest implements WithAssertions {
                 .withMessageContaining(dir.toString());
     }
 
+    // When opening a repo in a dir that is not a bare repo then an exception is thrown
+    @Test
+    void openRepo_whenRepoNotBare_thenThrowException() throws IOException, GitAPIException {
+        //given
+        final Path dir = nonBareRepo();
+        //then
+        assertThatExceptionOfType(InvalidRepositoryException.class)
+                .isThrownBy(() -> GitDB.openLocal(dir))
+                .withMessageContaining("Invalid GitDB repo")
+                .withMessageContaining("Not a bare repo")
+                .withMessageContaining(dir.toString());
+    }
+
+    private Path nonBareRepo() throws IOException, GitAPIException {
+        final Path dbDir = dirDoesNotExist();
+        Git.init().setGitDir(dbDir.toFile()).setBare(false).call();
+        return dbDir;
+    }
+
     // When opening a repo in a dir that is a bare repo then GitDb is returned
     @Test
     void openRepo_whenGitDB_thenReturnGitDB() throws IOException {