Track emulated symlinked directories recursively

[abishekgiri]

Description

This PR updates repository_ctx.symlink() invalidation tracking for emulated symlinks that target directories.

When Bazel cannot create a native symlink and falls back to copy-like behavior, directory targets now record a recursive DirTree input instead of a shallow File input. File targets keep the existing shallow watch behavior.

This change also adds unit coverage for emulated file and directory symlinks in StarlarkRepositoryContextTest.

Motivation

Directory-backed emulated symlinks were not tracked deeply enough for repository invalidation.

The fallback path always recorded a File input, which only captures that the directory exists. That is not sufficient to detect files being added, removed, or modified under the directory tree. Recording a recursive DirTree input fixes that behavior and adds regression coverage for it.

Build API Changes

No

Checklist

• I have added tests for the new use cases (if any).
• I have updated the documentation (if applicable).

Release Notes

RELNOTES: None

[abishekgiri]

Updated the invalidation tracking so emulated symlinks to directories now record recursive inputs, while emulated file symlinks keep the existing shallow file watch. Added focused unit coverage for both cases. Local Bazel validation on this machine is still blocked by the Xcode license gate from apple_support.

[bharadwaj08-one]

@abishekgiri Could you please take a look at the failing checks?

[abishekgiri]

@abishekgiri Could you please take a look at the failing checks?

I traced the failing presubmits from Buildkite build #32714 to one shared strict-deps issue in StarlarkRepositoryContextTest, not 15 unrelated failures.

The new test path references DirectoryTreeDigestValue, but StarlarkTests_lib was missing the direct dep on //src/main/java/com/google/devtools/build/lib/skyframe:directory_tree_digest_value. I pushed 6c4be441b0 to add that missing dep in src/test/java/com/google/devtools/build/lib/bazel/repository/starlark/BUILD.

A targeted local bazel test //src/test/java/com/google/devtools/build/lib/bazel/repository/starlark:StarlarkTests --test_filter='.*EmulatedSymlink.*' --test_output=errors no longer surfaces the strict-deps error. The remaining local blocker here is the machine-wide Xcode license issue (xcrun code 69), so I’m waiting on the fresh Buildkite rerun to confirm CI.

[meteorcloudy]

Please update PR description according to our PR template

[abishekgiri]

@meteorcloudy Updated the PR description to follow Bazel’s template. Thanks!

also http_file: add root BUILD to improve error when referencing repo root
#29136 got closed even after you approved it without any explanation