build: drop /XO from robocopy auto-deploy

[SkrubbySkrubInAShrub]

Summary

• Drop /XO (eXclude Older) from the three robocopy invocations under AUTO_PLUGIN_DEPLOYMENT so changed source files actually reach the install
• Update inline comments to document the trap (any prior touch to dest can give it a newer mtime than git-checkout source, which silently disables deploy)

Why

/XO skips files where source is older than dest. In a normal git workflow that's usually safe — but as soon as anything else touches the destination (a manual cp during debugging, a package install, even a previous build that ran later in wall time than the source's git checkout), dest gets a newer mtime and /XO then refuses to overwrite even when the source file's size and content have changed.

Concrete failure that prompted this

While debugging SLF I had RunGrass.hlsl fixed in source (commit f11bfaa32, source size 33287 bytes with the corrected ShadowSampling include order), but the deployed file stayed at the previous 31877 bytes across multiple full builds. Mtime on dest (from a manual cp during earlier diagnostics) was newer than the git-checkout mtime on source, so /XO skipped the copy. Grass and Particle pixel shaders failed to compile in-game:

LightLimitFix/LightLimitFix.hlsli(85,3-28): error X3000: unrecognized identifier 'DirectionalShadowLightData'

Same shape of bug can hit any contributor who: tests a package install over their dev build, copies files manually for any reason, or just has clock skew across filesystem boundaries.

What this changes

Before	After
`/E /XD ... /COPY:DAT /XO /R:1 /W:1 ...`	`/E /XD ... /COPY:DAT /R:1 /W:1 ...`

Without /XO, robocopy uses its default name + size + timestamp delta — copies whenever any of those differ. Catches both newer-source and size-mismatch cases. The git-HEAD-change block above the deploy commands already clears AIO and deploy stamps on branch switch, so the bulk-redeploy story is unchanged.

Trade-off

The property /XO nominally provided ("don't clobber files the user intentionally edited in-game between builds at the same HEAD") was fragile anyway — broken by any external touch to dest. Removing it costs ~100ms of extra IO per build on unchanged files (robocopy still skips matching name+size+timestamp). Correctness wins.

Test plan

• `BuildRelease.bat ALL-WITH-AUTO-DEPLOYMENT` produces a deployed install that matches `build//aio` byte-for-byte
• Manually `touch` a file in the deployed install to give it a newer mtime, rebuild, confirm the source file overwrites it
• Verify unchanged files still skip on subsequent builds (robocopy's default behavior)

🤖 Generated with Claude Code

Summary by CodeRabbit

• Bug Fixes
  • Fixed incremental deployment logic to properly detect and copy updated content, resolving an issue where destination file timestamps could prevent source changes from being applied during builds.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

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Run ID: ff3f5d2c-3d8f-46ac-ab2a-a0a4412ebca0

📥 Commits

Reviewing files that changed from the base of the PR and between 6c369ad and 734c3e2.

📒 Files selected for processing (1)

• CMakeLists.txt

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📝 Walkthrough

Walkthrough

This PR updates the AUTO_PLUGIN_DEPLOYMENT CMake logic to remove the /XO robocopy flag from per-build AIO and shader copies, preventing changed source files from being skipped when destination timestamps are newer. Supporting comments clarify the timestamp-based behavior and the role of git-HEAD-change clearing.

Changes

Robocopy Deployment Flag Fix

Layer / File(s)	Summary
Robocopy timestamp behavior rationale CMakeLists.txt	Comments updated to explain how /XO can skip copying when destination mtimes are newer, and how the git-HEAD-change block ensures stale timestamps don't prevent redeploy on repository changes.
Incremental deployment flag removal CMakeLists.txt	Main incremental robocopy invocation removes /XO flag with detailed rationale about preventing timestamp-based copy skipping during per-build deployment.
Shader deployment flag removals CMakeLists.txt	Both fast shader-only and full shader robocopy invocations remove /XO flag, applying the same timestamp-prevention fix across shader-specific deployment paths.

Estimated code review effort

🎯 2 (Simple) | ⏱️ ~10 minutes

Possibly related PRs

• community-shaders/skyrim-community-shaders#2306: Both PRs modify CMakeLists.txt's Windows AUTO_PLUGIN_DEPLOYMENT robocopy-based incremental deploy behavior for AIO/shader copying—build: fix windows auto deploy script #2306 changes how the robocopy wrapper is invoked and stages shader copies to avoid race issues, while the main PR changes the robocopy flags (removing /XO) in the same deploy steps to ensure changed sources aren't skipped.
• community-shaders/skyrim-community-shaders#1756: The main PR's CMake changes adjust the robocopy invocation flags used by the fast shader-only and full shader AUTO_PLUGIN_DEPLOYMENT deploy paths, which are exactly the shader deployment workflows/targets (e.g., COPY_SHADERS/shader-only vs shader-full stamps) introduced and wired up in #1756.
• community-shaders/skyrim-community-shaders#2251: Both PRs modify the same CMakeLists.txt deployment/staging logic under AUTO_PLUGIN_DEPLOYMENT—build: force AIO rebuild on HEAD change or manual delete #2251 clears AIO + deploy/shader stamp files on HEAD/change to force redeploy, while the main PR changes the subsequent robocopy copy steps (removing /XO for AIO/shader copies) to prevent timestamp-based skipping—so they directly touch the same incremental deployment control flow.

Suggested reviewers

• doodlum
• jiayev

Poem

🐰 A rabbit's robocopy ode:
Old flags that skipped with haughty pride,
Now /XO sits shuffled aside!
Timestamps yield to source's call—
Fresh shaders flow to victory hall. ✨

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title clearly and specifically summarizes the main change: removing the /XO flag from robocopy auto-deploy. It directly reflects the core modification in the changeset.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

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✨ Finishing Touches

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✅ A pre-release build is available for this PR:
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