Ensure ReflogWriter only works with a RefDirectory

The ReflogWriter constructor just took a Repository and called
getDirectory() on it to figure out the reflog dirs, but not all
Repository instances use this storage format for reflogs, so it's
incorrect to attempt to use ReflogWriter when there is not a
RefDirectory directly involved. In practice, ReflogWriter was mostly
only used by the implementation of RefDirectory, so enforcing this is
mostly just shuffling around calls in the same internal package.

The one exception is StashDropCommand, which writes to a reflog lock
file directly. This was a reasonable implementation decision, because
there is no general reflog interface in JGit beyond using
(Batch)RefUpdate to write new entries to the reflog. So to implement
"git stash drop <N>", which removes an arbitrary element from the
reflog, it's fair to fall back to the RefDirectory implementation.
Creating and using a more general interface is well beyond the scope of
this change.

That said, the old behavior of writing out the reflog file even if
that's not the reflog format used by the given Repository is clearly
wrong. Fail fast in this case instead.

Change-Id: I9bd4b047bc3e28a5607fd346ec2400dde9151730

1 files changed, 12 insertions, 3 deletions

diff --git a/org.eclipse.jgit/src/org/eclipse/jgit/api/StashDropCommand.java b/org.eclipse.jgit/src/org/eclipse/jgit/api/StashDropCommand.java
index e215bdf7d3..85e7b3d298 100644
--- a/org.eclipse.jgit/src/org/eclipse/jgit/api/StashDropCommand.java
+++ b/org.eclipse.jgit/src/org/eclipse/jgit/api/StashDropCommand.java
@@ -56,6 +56,7 @@ import org.eclipse.jgit.api.errors.JGitInternalException;
 import org.eclipse.jgit.api.errors.RefNotFoundException;
 import org.eclipse.jgit.errors.LockFailedException;
 import org.eclipse.jgit.internal.JGitText;
+import org.eclipse.jgit.internal.storage.file.RefDirectory;
 import org.eclipse.jgit.internal.storage.file.ReflogWriter;
 import org.eclipse.jgit.lib.ObjectId;
 import org.eclipse.jgit.lib.Ref;
@@ -68,6 +69,9 @@ import org.eclipse.jgit.util.FileUtils;
 
 /**
  * Command class to delete a stashed commit reference
+ * <p>
+ * Currently only supported on a traditional file repository using
+ * one-file-per-ref reflogs.
  *
  * @see <a href="http://www.kernel.org/pub/software/scm/git/docs/git-stash.html"
  *      >Git documentation about Stash</a>
@@ -84,6 +88,10 @@ public class StashDropCommand extends GitCommand<ObjectId> {
 	 */
 	public StashDropCommand(Repository repo) {
 		super(repo);
+		if (!(repo.getRefDatabase() instanceof RefDirectory)) {
+			throw new UnsupportedOperationException(
+					JGitText.get().stashDropNotSupported);
+		}
 	}
 
 	/**
@@ -205,10 +213,11 @@ public class StashDropCommand extends GitCommand<ObjectId> {
 			return null;
 		}
 
-		ReflogWriter writer = new ReflogWriter(repo, true);
+		RefDirectory refdb = (RefDirectory) repo.getRefDatabase();
+		ReflogWriter writer = new ReflogWriter(refdb, true);
 		String stashLockRef = ReflogWriter.refLockFor(R_STASH);
-		File stashLockFile = writer.logFor(stashLockRef);
-		File stashFile = writer.logFor(R_STASH);
+		File stashLockFile = refdb.logFor(stashLockRef);
+		File stashFile = refdb.logFor(R_STASH);
 		if (stashLockFile.exists())
 			throw new JGitInternalException(JGitText.get().stashDropFailed,
 					new LockFailedException(stashFile));