ci: build on push only for client-facing changes

Push builds used to rebuild both platforms for any Jenkinsfile or ci/jenkins/
change, and every build publishes to the downloads page. Now only
DorkNet.ClientMod/ and tools/build_pc.py (PC) or DorkNet.Quest/ (Quest)
changes rebuild, and Markdown never counts; CI-only changes take a manual
run. The README gives the matching Git path filter for the job, so other
pushes don't start a run at all.

Jenkinsfile

@@ -9,8 +9,9 @@
 // from the agent's environment (ARCHIVE_PC_REPO / ARCHIVE_QUEST_REPO), each
 // overridable per run. A build is picked by snapshot tags.
 //
-// On a push, only the platforms whose code changed are rebuilt. A manual run
-// picks the platforms with PLATFORMS. See ci/jenkins/README.md.
+// A push builds only the platforms whose client code changed (never for
+// docs or CI-only changes). A manual run picks the platforms with PLATFORMS.
+// See ci/jenkins/README.md.
 //
 // Finished builds are renamed for players and published to the downloads bucket
 // (ci/downloads) unless PUBLISH_DOWNLOADS is off. The build scripts keep their
@@ -76,10 +77,15 @@ pipeline {
             for (cs in currentBuild.changeSets) {
               for (entry in cs.items) changed.addAll(entry.affectedPaths)
             }
-            def touches = { prefixes -> changed.any { p -> prefixes.any { p.startsWith(it) } } }
-            def common = ['Jenkinsfile', 'ci/jenkins/']
-            buildPc = touches(common + ['DorkNet.ClientMod/', 'tools/build_pc.py'])
-            buildQuest = touches(common + ['DorkNet.Quest/'])
+            // Only client-facing changes rebuild (and so republish) a
+            // platform; Markdown doesn't count. The job's Git path filter
+            // uses the same paths, so other pushes don't start a run at all.
+            // A CI-only change (Jenkinsfile, ci/) takes a manual run.
+            def touches = { prefixes ->
+              changed.any { p -> !p.toLowerCase().endsWith('.md') && prefixes.any { p.startsWith(it) } }
+            }
+            buildPc = touches(['DorkNet.ClientMod/', 'tools/build_pc.py'])
+            buildQuest = touches(['DorkNet.Quest/'])
             echo "Push build; ${changed.size()} changed file(s)"
           } else {
             buildPc = params.PLATFORMS in ['both', 'pc']

ci/jenkins/README.md

@@ -60,10 +60,18 @@ Resolve a table for another build locally with `build.py build --dump-cs`.
 
 ## Triggers
 
-- **Push** to the branch (GitHub webhook) rebuilds only what changed:
-  - `DorkNet.ClientMod/` and the PC scripts rebuild PC;
+- **Push** to the branch (GitHub webhook) builds only for client-facing
+  changes, and only the platform they touch:
+  - `DorkNet.ClientMod/` and `tools/build_pc.py` rebuild PC;
   - `DorkNet.Quest/` rebuilds Quest;
-  - `Jenkinsfile` and `ci/jenkins/` rebuild both.
+  - Markdown files never count; server, docs and CI-only pushes (including
+    the `Jenkinsfile` and `ci/`) build nothing. Run those manually.
+
+  Set the same filter on the job so other pushes don't start a run at all:
+  under the job's **Git** source, add **Additional Behaviours → Polling
+  ignores commits in certain paths** with included regions
+  `DorkNet[.]ClientMod/.*`, `DorkNet[.]Quest/.*`, `tools/build_pc[.]py` (one
+  per line) and excluded region `.*[.]md`.
 - **Build with Parameters** runs a manual build:
   - `PLATFORMS` (both / pc / quest), and `PC_FULL_CLIENT` for the full PC client;
   - snapshot tags, and per-run repository overrides;