3 PARENT_SHA
=$
(git show-ref
-s refs
/heads
/gh-pages
)
4 DOC_SHA
=$
(git ls-tree
-d HEAD doc |
awk '{print $3}')
5 NEW_COMMIT
=$
(echo "Auto-update docs." | git commit-tree
$DOC_SHA -p $PARENT_SHA)
6 git update-ref refs
/heads
/gh-pages
$NEW_COMMIT
