Add a GitHub action to create version tags

The intended process is that we create tags regularly on the
GitHub mirror. Then we will have a separate action that
runs on tag to publish to NPM.

Bug: 442357424
Change-Id: Id71435785a5e601ebd405e64e0bd4577e38cf042
Reviewed-on: https://chromium-review.googlesource.com/c/devtools/devtools-frontend/+/6910793
Reviewed-by: Mathias Bynens <mathias@chromium.org>
Commit-Queue: Alex Rudenko <alexrudenko@chromium.org>

Author: OrKoN

.github/workflows/tag.yml

@@ -0,0 +1,34 @@
+name: Tag commits
+
+permissions:
+  contents: write
+
+on:
+  schedule:
+    # Run everyday at: https://crontab.guru/#0_6_*_*_*.
+    - cron: '0 6 * * *'
+  workflow_dispatch:
+
+jobs:
+  tag-commits:
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v5
+      - name: Get devtools version
+        id: devtools_version
+        shell: bash
+        run: devtools_version.sh
+      - name: Create tag
+        uses: actions/github-script@v7
+        # This can fail if the tag exists but this is expected.
+        continue-on-error: true
+        env:
+          TAG: ${{ steps.devtools_version.outputs.tag }}
+        with:
+          script: |
+            await github.rest.git.createRef({
+              owner: context.repo.owner,
+              repo: context.repo.repo,
+              ref: 'refs/tags/' + process.env.TAG,
+              sha: context.sha
+            });

scripts/devtools_version.sh

@@ -0,0 +1,25 @@
+#!/bin/bash
+
+# This script outputs the current DevTools version (e.g., `v1.0.1509326`) for
+# GitHub Actions to apply as a git tag (see tag.yml).
+
+# Adapted from
+# https://github.com/paulirish/npm-publish-devtools-frontend/blob/bc782b47c46c5fa4487ab2c46429a908a3501af2/publish-devtools-package-to-npm.sh
+# which evolved over 10 years.
+
+# this is the chrome-for-testing version string, eg 131.0.6752.0
+chrome_version="$(cat DEPS | grep "'chrome'" | head -n1 | sed "s/[^0-9.]//g")"
+
+# Find most recent roll of chromium INTO devtools-frontend standalone.
+#   NOTE: this isn't exactly the same as when frontend was rolled into chromium. But.. it shouldn't make a huge difference for these purposes.. :)
+chromium_commit_position=$(curl "https://chromiumdash.appspot.com/fetch_releases?platform=Mac" --silent | jq --arg chrome_version "$chrome_version" '.[] | select(.version == $chrome_version).chromium_main_branch_position')
+
+# verify we have a real number
+re='^[0-9]+$'
+if ! [[ $chromium_commit_position =~ $re ]] ; then
+   echo "error: Not a number" >&2; exit 1
+fi
+
+tag="v1.0.$chromium_commit_position"
+echo $tag
+echo "tag=$tag" >> "$GITHUB_OUTPUT"