[Only fetch darcs repositories that do not exist yet
clinton@unknownlamer.org**20090606191751
 Ignore-this: fdc23844b4c4429fd74ec747d46b7f22
] hunk ./scripts/utils.scm 31
-           (system* "darcs" "get"
-                    (first repo)
-                    (absolutize "external" (second repo))))
+           (let ((target (absolutize "external" (second repo))))
+             (if (not (file-exists? target))
+                 (system* "darcs" "get"
+                          (first repo)
+                          target))))