Cannot merge : merging into / resulted in conflicts. Rebase…

Error message

Cannot merge {branch_name}: merging into {fetch_remote_name}/{target_branch_name} resulted in conflicts.{detail} Rebase {branch_name} onto the target and resolve, then re-run `but merge {branch_name}`.

What it means

When landing, the library performs a trial merge of the branch into the remote target branch. If that merge produces conflicts, it cannot complete the landing automatically and refuses, listing conflicting paths and instructing the user to rebase first.

Solutions

Rebase the branch onto the latest target branch and resolve conflicts manually (`but pull --branch` / `git rebase origin/main`), then re-run `but merge <branch>`
Fetch first to make sure the conflict isn't against a stale view of the target, then retry
If conflicts are unwanted local edits, drop or rework the offending commits in the branch before landing

Example fix

# before
but merge feature-x
# error: merging into origin/main resulted in conflicts. Conflicting paths: src/app.rs.

# after
but pull --branch feature-x
git rebase origin/main  # resolve conflicts
but merge feature-x

Defensive patterns

Strategy: retry

Validate before calling

// dry-run merge check
git fetch origin
let merge_ok = std::process::Command::new("git")
    .args(["merge-tree", &feature_oid.to_string(), &target_oid.to_string()])
    .output()?.status.success();
if !merge_ok { println!("rebase branch onto target first"); }

Try / catch

match land_result {
    Err(e) if e.to_string().contains("resulted in conflicts") => {
        let detail = e.to_string();
        rebase_and_resolve(extract_conflict_paths(detail));
        retry_land();
    }
    other => other?,
}

Prevention

Rebase frequently to keep branches close to the target
Fetch immediately before landing so conflicts are detected against fresh remote state
Keep branches short-lived and land them promptly to minimize drift

When it happens

Trigger: Calling `but merge <branch>` where the branch's changes overlap/conflict with changes already on `{fetch_remote}/{target_branch}` — the internal `merge` tree operation returns conflicts with non-empty conflicting paths.

Common situations: A teammate merged competing changes to the same files after your branch diverged; long-lived branch that drifted far from the target; refactoring on both sides touching identical lines.

Understand the failure class

Background: "git command failed": what it means when a tool shells out to git and git exits non-zero — this error's family across 21 libraries.

Related errors

AI-assisted analysis of gitbutlerapp/gitbutler@58e5313667 (2026-09-18). Data as JSON: /api/errors/d0538b161b5389ec. Report an issue: GitHub.

Appendix: source

Thrown at crates/but-api/src/land/merge.rs:102

    let mut merge = repo.merge_trees(
        base_tree,
        our_tree,
        their_tree,
        repo.default_merge_labels(),
        merge_options,
    )?;
    if merge.has_unresolved_conflicts(unresolved) {
        let paths: Vec<String> = merge
            .conflicts
            .iter()
            .filter_map(|c| c.ours.location().to_str().ok().map(ToOwned::to_owned))
            .collect();
        let detail = if paths.is_empty() {
            String::new()
        } else {
            format!(" Conflicting paths: {}.", paths.join(", "))
        };
        bail!(
            "Cannot merge {branch_name}: merging into {fetch_remote_name}/{target_branch_name} \
             resulted in conflicts.{detail} Rebase {branch_name} onto the target and resolve, then \
             re-run `but merge {branch_name}`."
        );
    }
    let merged_tree = merge.tree.write()?.detach();

    // Build the 2-parent merge commit. Parent order is `[target, feature]` so `--first-parent`
    // mainline walks stay correct. `commit_signatures()` honors `gitbutler.gitbutlerCommitter`.
    let (author, committer) = repo.commit_signatures()?;
    let mut commit = gix::objs::Commit {
        tree: merged_tree,
        parents: [target_oid, feature_oid].into_iter().collect(),
        author,
        committer,
        encoding: None,
        message: format!("Merge branch '{branch_name}'").into(),
        extra_headers: Vec::new(),

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