[PATCH] revset: introduce feature revset for tracking in-progress work (issue4968)

[timeless]

>> 1. C is R or C is an ancestor of R
>> 2. C is not public
>> 3. C is not a merge commit
>> 4. C is not obsolete
>> 5. no bookmarks exist in [C, R) for C != R
>> 6. all commits in (C, R) are also within R for C != R
>>
> This is awfully specific. What are the use cases that you want to use this
> revset for?
>
> #3 why exclude merge commits if they met all the other criteria?

I assume the UC is:

o - wip() - tip
|
m
| \
| o - public() -- excluded by class 2
|
o - wip()

The merge w/ public isn't interesting to someone reviewing their work

I suppose a more interesting question is:

o - wip() - tip
|
m - significant merge
| \
| o - wip()
|  |
o | - wip()
| /
o - wip(origin)
|
o - public()

where you diverged from yourself in making a and b and you also made a
meaningful merge at the merge point due to conflicts.

He's assuming that this wouldn't happen. Namely, people shouldn't be
adding features in merges, just resolving differences, which aren't
interesting when they're reviewing what they've done.

> #5 this implies a certain usage of bookmarks (depending on what your use
> cases for feature() are)

It implies if you're interested in a different thing, you'd look at
wip(otherbookmark).

It's not an unreasonable methodology. It does mean that a bookmark
ends work on one thing and begins work on another, but I don't see
that as particularly unreasonable.