WIP: Porting to Nim.

treediff.pseudocode

@@ -0,0 +1,12 @@
+analyzeDir (tail call optimizable?)
+  count total # of files
+  for all files in directory
+    compute md5 checksum
+    create file entry: file obj, relative path, checksum
+    add entry to dictionary indexed by relative path
+    add entry to dictionary indexed by checksum
+    add entry to list of all entries
+    for each subdirectory, analyzeDir
+    return analysis
+
+