feat: support pipeline_branch param to load pipeline YAML from a specific git branch

[mehulparmariitr]

Description

Adds support for specifying which git branch to load the pipeline YAML from when executing a pipeline via MCP.

Problem

Passing pipelineBranchName to harness_execute was silently ignored. The queryParams map for the pipeline run action had no entry for it, so the value was placed in the YAML request body where Harness ignores it. Harness only reads pipelineBranchName as a URL query parameter.

Fix

Added pipeline_branch: "pipelineBranchName" to the queryParams mapping in src/registry/toolsets/pipelines.ts. Updated actionDescription and bodySchema.fields so the param is discoverable via harness_describe.

Usage

harness_execute(
  url="<pipeline URL>",
  action="run",
  params={"pipeline_branch": "feature/my-fix"}
)

When pipeline_branch is omitted, ?pipelineBranchName= is not sent and Harness falls back to the pipeline's configured default branch.

Tests

6 new tests covering the fix:

Test	Location	What it verifies
pipeline execute sends pipeline_branch as ?pipelineBranchName= query param	tests/registry/registry.test.ts	Registry queryParams mapping
pipeline execute omits pipelineBranchName when pipeline_branch not provided	tests/registry/registry.test.ts	Param absent when not passed
pipeline execute omits pipelineBranchName when pipeline_branch is empty string	tests/registry/registry.test.ts	Empty string treated as absent (guards value !== "" filter)
pipeline execute sends both pipeline_branch and inputs.branch independently	tests/registry/registry.test.ts	pipelineBranchName goes to URL query string; inputs.branch expands into body build structure — no interference
passes pipeline_branch from params as ?pipelineBranchName= query param	tests/tools/tool-handlers.test.ts	Full tool handler path
pipeline_branch coexists with other params without clobbering	tests/tools/tool-handlers.test.ts	Multi-key params Object.assign path; pipeline_branch + module both arrive on the POST

Type of Change

• Bug fix
• New feature

Checklist

• Tests pass
• Typecheck passes