You could probably org-map your way
through the subtrees and export each one by calling
(org-export-as 'html t)
N.B. the subtreep setting in this call.
Thanks for the tip. I ended up with this:
(let ((subtree-tags-to-export '("readme" "contributing"
"wikitcsh"))
;; If a subtree matches a tag, do not try to export further
;; subtrees separately that could be under that.
(org-use-tag-inheritance nil)
(org-export-with-toc nil) ;Do not export TOC
(org-export-with-tags nil)) ;Do not print tag names in exported files
(dolist (tag subtree-tags-to-export)
(let* ((exported-file-list (org-map-entries '(org-gfm-export-to-markdown nil :subtreep) tag))
;; The assumption is that for each tag, *only* one file is exported
(exported-file (when exported-file-list
(car exported-file-list))))
(when (string-match-p "\\`wiki.+" tag) ;Move the wiki files to the correct directory
(rename-file (expand-file-name exported-file eless-root-dir)
(expand-file-name exported-file eless-wiki-dir)
:ok-if-already-exists)))))