tigefa4u projects Trac

VcRefactoring: initialize merge tracking with SvnMerge

Follow-up to r4848, fix syntax of conditional comments for IE.

VcRefactoring: s/module.env/env/ where relevant.

Apply second patch from Peter, which moves the !RequestHandler to `trac.web.api.RequestProcessor` and refactors the Browser module to use it as well.

Applying my subsequent refactoring (introduction of !RequestHandler helper class)

Applying initial patch from Peter Dimov (trac-r4937-LogRequest.patch)

Restart the vc-refactoring branch

0.10.4dev: ported r4965 to stable (''improve concurrent resyncs, #4685 and #4043'')

Improve the repository resync, which now explicitly stores the youngest revision in the cache as metadata.

The new `sync()` method is now faster and also more robust.
Explicitly storing the `youngest_rev` addresses the efficiency concerns about the old `get_youngest_rev_from_cache()` method (#3837). That method is now only used once for automatically migrating environments to the new way, without requiring an explicit `resync`. It is otherwise deprecated and should be removed in the future.

The new scheme also takes lots of precautions to do the right thing in case of concurrent resync attempts. When a given thread accesses a repository, it will manage to sync none, some or all revisions. In any case, it will leave the sync() method with the notion of an usable and coherent youngest_rev, which will be used for the rest of the processing.

This changes fixes #4586 and is believed to fix #4043 as well.

Another error reporting improvement in case no database connection is available. This one is specifically needed in case the database connectivity is lost while the environment has already been in use (see also r4961).