gitbutlerapp/gitbutler

`mergiraf` merge driver seems to fail with exit code 256

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#10509 opened on Sep 30, 2025

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 (13 comments) (1 reaction) (1 assignee)Rust (19,787 stars) (862 forks)batch import
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Description

Originally on Discord.

Caused by:
    External merge driver failed with non-zero exit status ExitStatus(unix_wait_status(256)): GIT_DIR="/redacted-2/.git" GIT_WORK_TREE="/redacted-2" "/bin/sh" "-c" "mergiraf merge --git /redacted/.tmpeCLIAS /redacted/.tmp9grGSk /redacted/.tmppgWPKA -s \'\' -x \'\' -y \'\' -p \'work-ui/static/js/components/Header.tsx\' -l 7" "--"

The underlying configuration is:

[merge "mergiraf"]
    name = mergiraf
    driver = mergiraf merge --git %O %A %B -s %S -x %X -y %Y -p %P -l %L

It's unclear why it fails with exit status 256 at this time.

It's working in another clone, so it seems to be related to the mixup of the worktree directory, here /redacted-2 vs /redacted for tempfiles.

As a matter of fact, it appears to always create tempfiles in the /redacted directory, which usually leads to the failure.

The tempfiles are created from the CWD which is the reason for the sticky /redacted folder.

We know the merge driver process could be executed. And we know that it would provide stderr to the enclosing terminal.

Contributor guide

Tech stack
rust
Domain
backendcli
Issue type
bug
DifficultyEstimated implementation difficulty for a new contributor, from 1 for very small changes to 5 for expert-level work.
3
Estimated timeA rough time range for an experienced contributor to investigate, implement, test, and prepare a pull request.
half day
Activity statusHow available the issue appears right now: fresh, active, stale, blocked, or waiting on maintainer input.
active
ClarityHow clearly the issue explains the expected change, acceptance criteria, and next step.
mostly clear
Prerequisites
Rust programmingGit merge driversFile system basics
Newbie friendlinessA 1-100 score estimating how approachable this issue is for first-time contributors.
30
Research direction
Investigate the tempfile creation in gix merge/src/blob/platform/merge.rs line 129, which uses the current working directory (CWD) instead of the correct worktree directory. The merge driver process (lines 415-420) is executed from a different worktree, causing tempfiles to be placed in the wrong location. The fix should ensure tempfiles are created relative to the appropriate worktree path, possibly using environment variables or adjusting the CWD before creating tempfiles. Also review the stderr handling (lines 222-227) to capture any error output.