Auto merge of #22954 - Manishearth:tc-docs-split, r=jdm

Put the docs task into its own builder until it learns to behave

The latest rust update regressed rustdoc performance on servo a lot (6min to 37min), and now the tidy+unit+docs builder keeps timing out.

This splits out the doc task into its own thing until we can fix this.

r? @jdm

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etc/taskcluster/decision_task.py

@@ -30,7 +30,8 @@ def main(task_for):
         linux_wpt = lambda: None  # Shadows the existing top-level function
 
         all_tests = [
-            linux_tidy_unit_docs,
+            linux_tidy_unit,
+            linux_docs,
             windows_unit,
             macos_unit,
             magicleap_dev,
@@ -56,7 +57,7 @@ def main(task_for):
             # https://github.com/servo/saltfs/blob/master/homu/map.jinja
 
             "try-mac": [macos_unit],
-            "try-linux": [linux_tidy_unit_docs],
+            "try-linux": [linux_tidy_unit],
             "try-windows": [windows_unit],
             "try-magicleap": [magicleap_dev],
             "try-arm": [linux_arm32_dev, linux_arm64_dev],
@@ -148,10 +149,10 @@ def tidy_untrusted():
     )
 
 
-def linux_tidy_unit_docs():
+def linux_tidy_unit():
     return (
-        linux_build_task("Tidy + dev build + unit tests + docs")
-        .with_treeherder("Linux x64", "Tidy+Unit+Doc")
+        linux_build_task("Tidy + dev build + unit tests")
+        .with_treeherder("Linux x64", "Tidy+Unit")
         .with_script("""
             ./mach test-tidy --no-progress --all
             ./mach build --dev
@@ -165,7 +166,15 @@ def linux_tidy_unit_docs():
             ./etc/taskcluster/mock.py
             ./etc/ci/lockfile_changed.sh
             ./etc/ci/check_no_panic.sh
+        """)
+        .find_or_create("linux_tidy_unit." + CONFIG.git_sha)
+    )
 
+def linux_docs():
+    return (
+        linux_build_task("Docs")
+        .with_treeherder("Linux x64", "Doc")
+        .with_script("""
             ./mach doc
             cd target/doc
             git init
@@ -178,7 +187,6 @@ def linux_tidy_unit_docs():
         .find_or_create("docs." + CONFIG.git_sha)
     )
 
-
 def upload_docs():
     docs_build_task_id = decisionlib.Task.find("docs." + CONFIG.git_sha)
     return (