tigefa4u projects Trac

Ported [2969] to 0.9-stable (fixing #2777).

Gracefully handle invalid character entities in verbatim HTML. Closes #2777.

Autodetect big changesets and optimize their display.

When a changeset is deemed to be too big to be displayed in one page containing all the diffs, the actual diffs are simply not included in the view.

Instead, the modified file entries have a link pointing to a TracChangeset view that will contain only the changes affecting that file.

In order to detect big changesets, the following heuristic is used:
1. The sum of the sizes in bytes of the modified files (old ones + new ones) should not exceed the `max_diff_bytes` parameter
2. The total number of files in the changeset should not exceed the `max_diff_files` parameter.
3. If there's only one file modified, rule 1. is ignored and the diff content is always shown.

The following defaults are used:
{{{
[changeset]
max_diff_bytes = 10000000
max_diff_files = 1000
}}}

This should close #2343 and #2591.

Add support for `req.args.getlist()` and `req.args.getfirst()` to match the [http://docs.python.org/lib/node472.html higher level interface] of the CGI `FieldStorage` class. Closes #2846.

Moved `TracError` into the `trac.core` module (but importing from `trac.util` should continue to work).

Fixed the definition of a restricted changeset.

The restricted changeset for a path should only show
modified paths that are either:
* exactly the same as the given path,
* the directories above
* the files and folders below the path, if the path is a directory

Before the fix, the restricted changeset for e.g.
`trunk/README` would also show `trunk/README.tracd`,
and conversely.

WorkFlow:

* Merged log:trunk:2867:2963
* Removed dictionary hacks made redundant by WSGI merge.

* Under [wiki:TracModPython mod_python], you couldn't have multiple headers with the same name (e.g. `Set-Cookie`), which was the cause for #2843. That is now fixed by using `req.headers_out.add()` instead of dict-style assignment.
* Also under mod_python, when using a non-multithreaded MPM, the Trac environment wasn't being reused.
* Minor cleanup of session code.

No need to provide a default value, it's automatically pulled from {{{db_default.py}}}.

Migrated [wiki:TracStandalone tracd] to use the Python {{{optparse}}} module, and moved all the actual code into {{{trac.web.standalone}}}.