prompt push fails with 409 conflict when updating existing prompt - missing parent commit option

[codekiln]

Description

When using langstar prompt push to update an existing prompt repository, the command fails with a 409 conflict error:

ℹ Checking if repository -/<prompt-name> exists...
✓ Repository exists
ℹ Loading schema file...
ℹ Validating schema...
ℹ ✓ Schema valid
ℹ Pushing structured prompt to -/<prompt-name> (method: json_schema)...
Error: API error: 409 - {"error":"Parent commit validation failed: reference ID <commit-hash>"}

Steps to Reproduce

1. Pull an existing prompt: langstar prompt pull -- "-/<prompt-name>"
2. Modify the schema (e.g., update a field type)
3. Attempt to push the updated prompt:

   langstar prompt push \
     -o "-" \
     -r "<prompt-name>" \
     -t "$(cat template.txt)" \
     -i "var1,var2,var3" \
     --schema updated_schema.json

Expected Behavior

Either:

1. The push should automatically fetch the latest commit hash and use it as the parent commit
2. There should be a --parent-commit <hash> option to specify the parent commit
3. There should be a --force option to override versioning

Current Behavior

The push fails with a 409 conflict error because the LangSmith API requires a valid parent commit reference when updating an existing prompt.

Suggested Solution

Add one or more of:

• --parent-commit <HASH> option to specify the parent commit explicitly
• --auto-parent flag to automatically fetch and use the latest commit as parent
• --force flag to override (with appropriate warnings)

Environment

• langstar version: (latest)
• OS: macOS