tip.cuelang.org: apply the stored patch

This adds a step near the end of CI that unconditionally checks that the
patch stored at internal/patch/tip.diff still applies to the repo
successfully. CI performs this check by actually applying the patch via
_scripts/tipPatchApply.bash - any use of this script leaves the repo in
a modified/dirty state.

The patch contains changes that make the site compatible with the tip of
cue-lang/cue's default branch.

A follow-up CL will:

1. add a CI step that runs whenever the default branch of this repo is
   updated and:
   - forces the site to use the tip of cue-lang/cue
   - invokes ./_scripts/regenPostInfraChange.bash
   - checks that the site builds successfully

Later changes might also:

2. publish the site (e.g. to the as-yet-unestablished tip.cuelang.org)
   after (1) succeeds
3. replicate (1) and (2) any time the default branch of cue-lang/cue is
   updated;
4. push the working trees generated by (1) and/or (3) to a long-running
   CL, so that the delta is visible/downloadable/etc.

Signed-off-by: Paul Jolly <[email protected]>
Change-Id: I8fe2461cd4caa24d12fda7361b5205ae5c871640
Dispatch-Trailer: {"type":"trybot","CL":1200804,"patchset":8,"ref":"refs/changes/04/1200804/8","targetBranch":"master"}

.github/workflows/trybot.yaml

@@ -232,3 +232,5 @@ jobs:
           ALGOLIA_ADMIN_KEY: ${{ secrets.ALGOLIA_INDEX_KEY }}
           ALGOLIA_INDEX_NAME: cuelang.org
           ALGOLIA_INDEX_FILE: ../_public/algolia.json
+      - name: 'tip.cuelang.org: Apply tip''s patch, checking that it applies cleanly'
+        run: _scripts/tipPatchApply.bash

_scripts/tipPatchApply.bash

@@ -0,0 +1,24 @@
+#!/usr/bin/env bash
+set -euo pipefail
+
+# Usage:
+#     tipPatchApply.bash
+#
+# tipPatchApply applies the patch stored at $patchPath to the current git
+# working tree and index. This patch is intended to make the cuelang.org site
+# compatible with the tip version of cue-lang/cue.
+
+# cd to the parent directory to that containing the script
+cd "$( cd "$( dirname "${BASH_SOURCE[0]}" )" >/dev/null 2>&1 && pwd )/.."
+
+patchPath=$(./_scripts/tipPatchPath.bash)
+
+# We must be in a clean state first
+if test ! -z "$(git status --porcelain)"
+then
+	echo "working tree is not porcelain"
+	exit 1
+fi
+
+# --index: working tree and index must be identical.
+git apply --index $patchPath

_scripts/tipPatchGenerate.bash

@@ -0,0 +1,18 @@
+#!/usr/bin/env bash
+set -euo pipefail
+
+# Usage:
+#     tipPatchGenerate.bash
+#
+# tipPatchGenerate takes the current state of the working tree and stores its
+# diff against HEAD at $patchPath. This is intended to ease the ongoing,
+# repeated generation of the patch that makes the repo compatible with the tip
+# of cue-lang/cue.
+
+# cd to the parent directory to that containing the script
+cd "$( cd "$( dirname "${BASH_SOURCE[0]}" )" >/dev/null 2>&1 && pwd )/.."
+
+patchPath="$(./_scripts/tipPatchPath.bash)"
+
+# ":^x" excludes changes to "x" from the diff.
+git diff HEAD -- . ":^$patchPath" >"$patchPath"

_scripts/tipPatchPath.bash

@@ -0,0 +1,10 @@
+#!/usr/bin/env bash
+set -euo pipefail
+
+# Usage:
+#     tipPatchPath.bash
+#
+# tipPatchPath prints the path of the patch file that makes the repo compatible
+# with the tip of cue-lang/cue, relative to the repo root.
+
+echo "internal/patch/tip.diff"

internal/ci/github/trybot.cue

@@ -248,6 +248,11 @@ workflows: trybot: _repo.bashWorkflow & {
 					ALGOLIA_INDEX_FILE: "../_public/algolia.json"
 				}
 			},
+
+			json.#step & {
+				name: "tip.cuelang.org: Apply tip's patch, checking that it applies cleanly"
+				run:  "_scripts/tipPatchApply.bash"
+			},
 		]
 	}
 

internal/patch/tip.diff

@@ -0,0 +1,13 @@
+diff --git a/playground/_scripts/revendorToolsInternal.bash b/playground/_scripts/revendorToolsInternal.bash
+index 771d24ec..ea3def82 100755
+--- a/playground/_scripts/revendorToolsInternal.bash
++++ b/playground/_scripts/revendorToolsInternal.bash
+@@ -29,7 +29,7 @@ popd > /dev/null
+
+ # TODO this is very fragile - we need to move away from this to a proper
+ # dependency-based approach to minimal copy
+-for i in "" filetypes encoding third_party/yaml encoding/yaml astinternal cueexperiment envflag source
++for i in "" filetypes encoding encoding/yaml astinternal cueexperiment envflag source
+ do
+ 	rsync -a --relative --delete $td/$path@$version/internal/./$i/ ./internal/cuelang_org_go_internal/
+ 	find ./internal/cuelang_org_go_internal/$i -mindepth 1 -maxdepth 1 -type d -exec rm -rf {} +