Megatest

      (lambda (varval)
	(let ((var (car varval))
	      (val (cdr varval)))
	  (if incremental (exec (sql db "DELETE FROM envvars WHERE context=? AND var=?") context var))
	  (exec (sql db "INSERT INTO envvars (context,var,val) VALUES (?,?,?)") context var val)))
	(get-environment-variables)))))

;; merge contexts in the order given
;;  - each context is applied in the given order
;;  - variables in the paths list are split on the separator and the components
;;    merged using simple delta addition
;;    returns a hash of the merged vars
;;
(define (env:merge-contexts db basecontext contexts paths)
  (let ((result (make-hash-table)))
    (for-each
     (lambda (context)
       (query
	(for-each-row
	 (lambda (row)
	   (let ((var  (car row))
		 (val  (cadr row)))
	     (hash-table-set! result var 
			      (if (and (hash-table-ref/default results var #f)
				       (assoc var paths)) ;; this var is a path and there is a previous path
				  (let ((sep (cadr (assoc var paths))))
				    (env:merge-path-envvar sep (hash-table-ref results var) valb))
				  valb)))))
	(sql db "SELECT var,val FROM envvars WHERE context=?")
	context))
     contexts)
    result))

;;  get list of removed variables between two contexts
;;
(define (env:get-removed db contexta contextb)
  (let ((result (make-hash-table)))
    (query
     (for-each-row
      (lambda (row)
	(let ((var  (car row))
	      (val  (cadr row)))
	  (hash-table-set! result var valb))))
     (sql db "SELECT var,val FROM envvars WHERE context=? AND var NOT IN (SELECT var FROM envvars WHERE context=?)")
     contexta contextb)
    result))

;;  get list of variables added to contextb from contexta
;;
(define (env:get-added db contexta contextb)
  (let ((result (make-hash-table)))
    (query
     (for-each-row
      (lambda (row)
	(let ((var  (car row))
	      (val  (cadr row)))
	  (hash-table-set! result var valb))))
     (sql db "SELECT var,val FROM envvars WHERE context=? AND var NOT IN (SELECT var FROM envvars WHERE context=?)")
     contextb contexta)
    result))

;;  get list of variables in both contexta and contexb that have been changed
;;
(define (env:get-changed db contexta contextb)
  (let ((result (make-hash-table)))
    (query
     (for-each-row
      (lambda (row)
	(let ((var  (car row))
	      (val  (cadr row)))
	  (hash-table-set! result var val))))
     (sql db "SELECT var,val FROM envvars WHERE context=? AND val != (SELECT val FROM envvars WHERE var=? AND context=?)")
     contexta contextb))
  result)

;;
(define (env:blind-merge l1 l2)
  (if (null? l1) l2
      (if (null? l2) l1
	  (cons (car l1) (cons (car l2) (env:blind-merge (cdr l1) (cdr l2)))))))

;; given a before and an after envvar calculate a new merged path
;;
(define (env:merge-path-envvar separator patha pathb)
  (let* ((patha-parts  (string-split patha separator))
	 (pathb-parts  (string-split pathb separator))
	 (common-parts (lset-intersection equal? patha-parts pathb-parts))
	 (final        (delete-duplicates ;; env:blind-merge 
			(append pathb-parts common-parts patha-parts))))
;;     (print "BEFORE:   " (string-intersperse patha-parts  "\n       "))
;;     (print "AFTER:    " (string-intersperse pathb-parts  "\n       "))
;;     (print "COMMON:   " (string-intersperse common-parts "\n       "))
    (string-intersperse final separator)))

(define (env:process-path-envvar varname separator patha pathb)



  (let ((newpath (env:merge-path-envvar separator patha pathb)))
    (setenv varname newpath)))

(define (env:have-context db context)
  (> (query fetch-value (sql db "SELECT count(id) FROM envvars WHERE context=?") context)
     0))

;; this is so the calling block does not need to import sql-de-lite
(define (env:close-database db)
  (close-database db))

		 (db      (env:open-db fname)))
	    (env:save-env-vars db context)
	    (env:close-database db)
	    (set! *didsomething* #t))
	  (begin
	    (debug:print 0 "ERROR: Parameter to -envcap should be <filename>=<context>. E.G. envdat=original, got: " envcap)
	    (set! *didsomething* #t)))))

;; delta "language" will eventually be res=a+b-c but for now it is just res=a-b 
;;
(let ((envdelta (args:get-arg "-envdelta")))
  (if envdelta
      (let ((match (string-match "([a-z]+)=([a-z\-,]+)" envdelta)))
	(if match
	    (let* ((resctx    (cadr match))
		   (equn      (caddr match))
		   (parts     (string-split equn "-"))
		   (minuend   (car parts))
		   (subtraend (cadr parts))
		   (
	    

;;======================================================================
;; Exit and clean up
;;======================================================================

(if *runremote* (close-all-connections!))