web: use PUBLIC_URL instead of package.json patch

This change simplify dashboard run playbook to fix sub-url serving of
ci build.

Change-Id: I58db8958894f2b51cca03752d9913ca11df5bba4

.zuul.yaml

@@ -45,6 +45,7 @@
     success-url: 'npm/html/'
     files:
       - web/.*
+      - playbooks/dashboard/.*
     vars:
       javascript_content_dir: "../zuul/web/static"
       zuul_work_dir: "{{ zuul.project.src_dir }}/web"

playbooks/dashboard/run.yaml

@@ -1,15 +1,4 @@
 - hosts: all
-  pre_tasks:
-    - name: Update homepage for sub directory deployment
-      replace:
-        path: '{{ zuul.project.src_dir }}/web/package.json'
-        regexp: '^{$'
-        replace: '{\n  "homepage": "./",'
-        # NOTE: using "./" is not enough to support html5 links, even with
-        # rewrite rules for unknown files, accessing 'job/devstack' will make
-        # the dashboard load static files from 'job/static/...'
-        # This works for the preview dashboard that can only be loaded from the
-        # npm/html directory anyway.
   roles:
     - revoke-sudo
     - set-zuul-log-path-fact
@@ -17,3 +6,9 @@
       npm_command: build
   environment:
     REACT_APP_ZUUL_API: "{{ zuul_api_url }}/api/"
+    PUBLIC_URL: './'
+    # NOTE: using "./" is not enough to support html5 links, even with
+    # rewrite rules for unknown files, accessing 'job/devstack' will make
+    # the dashboard load static files from 'job/static/...'
+    # This works for the preview dashboard that can only be loaded from the
+    # npm/html directory anyway.