hgweb.cgi and hgwebdir.cgi fixes/cleanups for user configurable parts:
- "import os" was missing in hgwebdir.cgi, added to comments for both script.
- HGENCODING has to be set before importing hgweb, otherwise you'll get
mixed encoding in changelog vs. file content/diffs.
- "import sys" is only needed when changing sys.path
- document purpose of cgitb.
% file replaced with directory
adding a
% should fail - would corrupt dirstate
abort: file named 'a' already in dirstate
% directory replaced with file
adding a/a
% should fail - would corrupt dirstate
abort: directory named 'a' already in dirstate
% directory replaced with file
adding b/c/d
% should fail - would corrupt dirstate
abort: directory named 'b' already in dirstate