fix(trail): fetch existing remote branch before create

1fd4f9f→main·

dipree·4w ago·1 file·+35 added/-11 removed

Address PR review feedback:

• validate branch names before trail create reaches git subcommands
• reject leading-dash branch names before invoking git
• when a requested branch is missing locally but already exists on origin, fetch it instead of creating a new local branch at HEAD
• make the non-fast-forward hint refer to the target branch

Sessions

b73b63b3e546View transcript

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Fix Trail Creation Branch Handling and ValidationPi·Opus 4.8·1 step](/content/gh/entireio/cli/session/019ed956-c81a-74d1-9437-9fb289e1410f#timeline-b73b63b3e546/index.html)

Changes

1

• cmd/entire/cli

• Mtrail_cmd.go+35/-11

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localBranchCreated := false
    var remoteBranchPushed bool

// Don't delete a remote branch we didn't create during cleanup.
    existedOnOrigin, existErr := branchExistsOnOrigin(branch)
    if existErr != nil {
        fmt.Fprintf(errW, "Warning: could not check whether branch %s already exists on origin: %v\n", branch, existErr)
        existedOnOrigin = true
    }

if needsCreation {
        if err := createBranch(repo, branch); err != nil {
            return fmt.Errorf("failed to create branch %q: %w", branch, err)
        }
        if existedOnOrigin {
            if err := fetchBranchFromOrigin(branch); err != nil {
                return fmt.Errorf("failed to fetch branch %q from origin: %w", branch, err)
            }
            localBranchCreated = true
            fmt.Fprintf(w, "Fetched branch %s from origin\n", branch)
        } else {
            if err := createBranch(repo, branch); err != nil {
                return fmt.Errorf("failed to create branch %q: %w", branch, err)
            }
            localBranchCreated = true
            fmt.Fprintf(w, "Created branch %s\n", branch)
        }
        localBranchCreated = true
        fmt.Fprintf(w, "Created branch %s\n", branch)
    } else if currentBranch != branch {
        fmt.Fprintf(w, "Note: trail will be created for branch %q (not the current branch)\n", branch)
    }
2 unmodified lines

// deliver it before creating the trail rather than letting the server
    // backfill it at the base tip.
    {
        // Don't delete a remote branch we didn't create during cleanup.
        existedOnOrigin, existErr := branchExistsOnOrigin(branch)
        if existErr != nil {
            fmt.Fprintf(errW, "Warning: could not check whether branch %s already exists on origin: %v\n", branch, existErr)
            existedOnOrigin = true
        }
        if err := pushBranchToOrigin(branch); err != nil {
            cleanupCreatedTrailBranch(repo, branch, localBranchCreated, false, errW)
            return fmt.Errorf("failed to push branch %q to origin: %w\nhint: the trail was not created because its branch could not be delivered to the remote.\n  - if this is an auth error, link your GitHub account and retry\n  - if this is a non-fast-forward, update your base (git fetch && git rebase) and retry", branch, err)
        }
        remoteBranchPushed = !existedOnOrigin
        fmt.Fprintf(w, "Pushed branch %s to origin\n", branch)
732 unmodified lines

}
}

func fetchBranchFromOrigin(branchName string) error {
    ctx, cancel := context.WithTimeout(context.Background(), 2*time.Minute)
    defer cancel()
    if err := ValidateBranchName(ctx, branchName); err != nil {
        return err
    }
    refspec := fmt.Sprintf("refs/heads/%%s:refs/heads/%%s", branchName, branchName)
    cmd := exec.CommandContext(ctx, "git", "fetch", "--no-tags", "origin", refspec)
    if output, err := cmd.CombinedOutput(); err != nil {
        return fmt.Errorf("%s: %w", strings.TrimSpace(string(output)), err)
    }
    return nil
}

// pushBranchToOrigin pushes a branch to the origin remote.
func pushBranchToOrigin(branchName string) error {
    ctx, cancel := context.WithTimeout(context.Background(), 2*time.Minute)