Close stdin after writing to prevent LFS smudge hang

[grub-basket]

Problem

RepoTask.flowStartProcess writes to the child process's stdin but never closes the write channel:

if stdin:
    process.write(stdin.encode("utf-8"))

DownloadLfsObjects pipes an LFS pointer into git lfs smudge, which reads stdin until EOF. With the write channel left open, smudge blocks forever waiting for EOF, the task never finishes, and the UI stays busy.

Repro

Open a diff of an LFS-tracked file whose object isn't cached locally → the smudge task hangs indefinitely.

Fix

Call process.closeWriteChannel() after writing stdin, so children that read to EOF terminate normally.

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Prepared with Claude Fable 5 (Low effort mode).

[jorio]

My understanding is git lfs smudge proceeds as soon as it has completed reading a pointer off stdin, whether it reaches EOF or not. This is why testLfsDownloadMissingObjectsToCache in our test suite passes without hanging. (Let me know if I'm wrong here!)

I think your fix can still prevent smudge from hanging if we pipe a pointer that it fails to parse completely, e.g. if it's an exotic version of LFS that expects a different format than what we supply.

In this case, fortunately our UI stays responsive and allows killing the underlying process if it takes too long. But having smudge fail instantly is still better UX, so your fix makes sense. Thanks!

[grub-basket]

You're right, and my "blocks forever" wording was too absolute — sorry about that. For a well-formed pointer, git lfs smudge doesn't need EOF: it reads only up to git-lfs's blob-size cutoff (~1 KB) to decide whether stdin is a pointer, and once it's decoded a valid one it proceeds without draining the rest of the pipe. That's exactly why testLfsDownloadMissingObjectsToCache doesn't hang.

Where closeWriteChannel() actually earns its keep is the case you identified: a pointer that smudge can't fully parse (an exotic/newer LFS format than we emit), where it keeps reading and would block waiting for EOF. It's also just tidier as defense-in-depth for any future stdin-reading child. Thanks for merging and for the careful reasoning.