Issue Summary

A git tree entry whose filename is pure whitespace (e.g. a single space character) is valid per git's object model. However, Bitbucket Mesh rejects it with IllegalArgumentException: A non-blank path is required, which surfaces as gRPC Status.UNKNOWN with no description. The repository becomes completely unbrowseable in the UI (500 / "UNKNOWN") on /browse, /files, and PR diffs until the entry is removed.

In previous versions of Bitbucket the /browse UI did handle whitespace only filenames, for example here is a screenshot from Bitbucket 7.6.23:

Analysis of the code suggest it is likely the regression first shipped in Bitbucket 8.0

Steps to Reproduce

1. Clone any existing repository from a Bitbucket DC instance
2. Create a regular file whose name is a single space character:

   echo "test" > ' '
   

3. Stage, commit, and push:

   git add ' '
   git commit -m "add whitespace-only filename"
   git push origin master
   

4. Browse the repository in the Bitbucket UI (/browse, /files, or any PR diff containing this commit)

Expected Results

Bitbucket should either:

• Display the entry (git considers it valid), or
• Return a meaningful gRPC error status with a descriptive message (e.g. INVALID_ARGUMENT: tree entry contains a blank filename) instead of UNKNOWN: null

Actual Results

The below exception is thrown in the Mesh log file (atlbitbucket-mesh.log or atlassian-bitbucket.log for embedded Mesh):

2026-05-12 23:03:05,659 WARN  [grpc-async:thread-4] admin AC5KMVRPx1383x262x2 @IGU6TEx1383x334x0 127.0.0.1 "ContentService/ListDirectory" (>1 <0) c.a.b.m.g.LoggingServerInterceptor RPC failed with an UNKNOWN error: null
java.lang.IllegalArgumentException: A non-blank path is required
  at com.atlassian.bitbucket.mesh.util.BuilderSupport.requireNonBlank(BuilderSupport.java:83)
  at com.atlassian.bitbucket.mesh.git.content.File$Builder.<init>(File.java:69)
  at com.atlassian.bitbucket.mesh.git.builder.lstree.DirectoryLsTreeStdioHandler.parse(DirectoryLsTreeStdioHandler.java:100)
  at com.atlassian.bitbucket.mesh.git.builder.lstree.DirectoryLsTreeStdioHandler.onStdout(DirectoryLsTreeStdioHandler.java:65)
  at com.atlassian.bitbucket.mesh.process.handler.LineDecoder.offerLine(LineDecoder.java:173)
  at com.atlassian.bitbucket.mesh.process.handler.LineDecoder.forEach(LineDecoder.java:128)
  at com.atlassian.bitbucket.mesh.process.handler.LineOutputAdapter.onBytes(LineOutputAdapter.java:125)
  at com.atlassian.bitbucket.mesh.process.handler.AbstractLineStdioHandler.onStdout(AbstractLineStdioHandler.java:72)
  at com.atlassian.bitbucket.mesh.git.content.DefaultContentManager.listDirectory(DefaultContentManager.java:117)
  at com.atlassian.bitbucket.mesh.git.GrpcContentService.lambda$listDirectory$0(GrpcContentService.java:61)
  at com.atlassian.bitbucket.mesh.execution.DefaultGrpcAsyncExecutor$GrpcTask.run(DefaultGrpcAsyncExecutor.java:62)

The error fires on every browse attempt. The entire repository is rendered unbrowseable for all users including admins.

Workaround

Remove the whitespace-only filename entry from the repository:

git rm -- ' '
git commit -m "remove whitespace-only filename"
git push origin master

The repository will become browseable again immediately after the push.