Default test-infra-ref to "main" in reusable job workflows (#8472)

The reusable `*_job*` / `build_wheels_*` / `_binary_upload` workflows
default `test-infra-ref` to `""` and pass it to `actions/checkout` as
`ref:`. An empty `ref` makes checkout do a "Determining the default
branch" REST call per job, which under large fan-out exhausts the org
GitHub App installation rate limit — the cause of the `Checkout
repository (pytorch/test-infra@)` failures in
[pytorch-gha-infra#1375](meta-pytorch/pytorch-gha-infra#1375).

Default it to `"main"` instead. `main` is what an empty ref already
resolves to, so no checkout behavior changes — checkout just skips the
default-branch lookup, dropping that call from the quota path for
consumers that don't pin their own ref.

Mitigation, not a full fix: it doesn't bound the fan-out or the separate
runner-registration quota (see #1375), and explicit `test-infra-ref: ''`
callers still override it. Draft for infra owners to confirm on CI.

Authored with assistance from Claude Code.

Author: huydhn

.github/workflows/_binary_upload.yml

@@ -17,7 +17,7 @@ on:
         type: string
       test-infra-ref:
         description: "Test infra reference to use"
-        default: ""
+        default: "main"
         type: string
       build-matrix:
         description: "Build matrix to utilize"

.github/workflows/build_wheels_linux.yml

@@ -17,7 +17,7 @@ on:
         type: string
       test-infra-ref:
         description: "Test infra reference to use"
-        default: ""
+        default: "main"
         type: string
       build-matrix:
         description: "Build matrix to utilize"

.github/workflows/build_wheels_macos.yml

@@ -17,7 +17,7 @@ on:
         type: string
       test-infra-ref:
         description: "Test infra reference to use"
-        default: ""
+        default: "main"
         type: string
       build-matrix:
         description: "Build matrix to utilize"

.github/workflows/build_wheels_windows.yml

@@ -17,7 +17,7 @@ on:
         type: string
       test-infra-ref:
         description: "Test infra reference to use"
-        default: ""
+        default: "main"
         type: string
       build-matrix:
         description: "Build matrix to utilize"

.github/workflows/linux_job.yml

@@ -56,7 +56,7 @@ on:
         type: string
       test-infra-ref:
         description: "Test infra reference to use"
-        default: ""
+        default: "main"
         type: string
       docker-image:
         description: Identifies the Docker image by name.

.github/workflows/linux_job_v2.yml

@@ -69,7 +69,7 @@ on:
         type: string
       test-infra-ref:
         description: "Test infra reference to use"
-        default: ""
+        default: "main"
         type: string
       use-custom-docker-registry:
         description: "Use the custom ECR registry. Applies only if build.sh exists in docker-build-dir."

.github/workflows/linux_job_v3.yml

@@ -70,7 +70,7 @@ on:
         type: string
       test-infra-ref:
         description: "Test infra reference to use"
-        default: ""
+        default: "main"
         type: string
       use-custom-docker-registry:
         description: "[Ignored on OSDC] Kept for compatibility with linux_job_v2.yml."

.github/workflows/macos_job.yml

@@ -56,7 +56,7 @@ on:
         type: string
       test-infra-ref:
         description: "Test infra reference to use"
-        default: ""
+        default: "main"
         type: string
       job-name:
         description: "Name for the job, which is displayed in the GitHub UI"

.github/workflows/mobile_job.yml

@@ -47,7 +47,7 @@ on:
         type: string
       test-infra-ref:
         description: Test infra reference to use
-        default: ''
+        default: "main"
         type: string
 
       # iOS-specific inputs

.github/workflows/windows_job.yml

@@ -56,7 +56,7 @@ on:
         type: string
       test-infra-ref:
         description: "Test infra reference to use"
-        default: ""
+        default: "main"
         type: string
       job-name:
         description: "Name for the job, which is displayed in the GitHub UI"