[gh-pages] Do full clone rather than shallow clone

This change causes the GH Pages build to do a full clone rather than a
shallow clone. This is necessary in order to get the correct timestamps
for all sources (see w3c#7898).

Otherwise, without this change, git doesn’t report accurate timestamps
for any sources; instead it reports the same timestamp for all of them —
which is apparently whatever the current time is when git creates the
(shallow) clone.

Author: sideshowbarker

.github/workflows/build-specs.yml

@@ -25,6 +25,8 @@ jobs:
 
     steps:
       - uses: actions/checkout@v3
+        with:
+          fetch-depth: 0
 
       - uses: actions/setup-python@v4
         with: