Current status of EOL support

[Ian Clatworthy]

As requested by Alex, here's the overall picture w.r.t.
EOL status.

Related code inside bzr.dev today:

1. Support for rules, configured globally in BZR_HOME/rules
2. Experimental formats, 1.12-preview and 1.12-preview-rich-root

Related patches in the review queue:

3. Content filtering
4. Tree-specific rules
5. Filtered views.

Note: (5) isn't directly related but both (3) and (5) require a
WorkingTree format bump so landing them in the same release
is most desirable.

Other related pieces mostly done:

6. bzr-eol plugin
7. bzr-keywords plugin

These need at least (3) landed. They also need some more
tests written, which I'm expecting to be easier after (4) lands.

Yet to be written stuff:

8. Patch to make 1.12 formats non-experimental
9. Branch/project specific rules
10. Branch dependency rules

(8) requires (3) and (5) landed into bzr.dev, and enough
testing by the community for us to be happy to make the
switch.

(9) probably requires a branch format bump so it would be
ideal if that were ready at the same time as the split
inventory (CHK) format lands.

(10) will let projects say stuff like "this branch requires
bzr 1.12 or later, and the bzr-eol plugin installed".

In summary, my hope is to get a new working-tree format
and related features production strength (and the default)
ASAP. In the worse case, that needs to happen no later
than the CHK branch format bump. I think a better outcome
though would be to spread out new feature risk by
changing working tree formats (in 1.12 I hope) and bringing
the CHK stuff in shortly after that.

Ian C.