revset: define successors revset
This revset returns all successors, including transit nodes and the source
nodes (to be consistent with existing revsets like "ancestors").
To filter out transit nodes, use `successors(X)-obsolete()`.
To filter out divergent case, use `successors(X)-divergent()-obsolete()`.
The revset could be useful to define rebase destination, like:
`max(successors(BASE)-divergent()-obsolete())`. The `max` is to deal with
splits.
There are other implementations where `successors` returns just one level of
successors, and `allsuccessors` returns everything. I think `successors`
returning all successors by default is more user friendly. We have seen
cases in production where people use 1-level `successors` while they really
want `allsuccessors`. So it seems better to just have one single revset
returning all successors by default to avoid user errors.
In the future we might want to add `depth` keyword argument to it and for
other revsets like `ancestors` etc. Or even build some flexible indexing
syntax [1] to satisfy people having the depth limit requirement.
[1]: https://www.mercurial-scm.org/pipermail/mercurial-devel/2017-July/101140.html
$ hg init
$ echo "added file1" > file1
$ echo "added file2" > file2
$ hg add file1 file2
$ hg commit -m "added file1 and file2"
$ echo "changed file1" >> file1
$ hg commit -m "changed file1"
$ hg -q log
1:08a16e8e4408
0:d29c767a4b52
$ hg id
08a16e8e4408 tip
$ hg update -C 0
1 files updated, 0 files merged, 0 files removed, 0 files unresolved
$ hg id
d29c767a4b52
$ echo "changed file1" >> file1
$ hg id
d29c767a4b52+
$ hg revert --all
reverting file1
$ hg diff
$ hg status
? file1.orig
$ hg id
d29c767a4b52
$ hg update
1 files updated, 0 files merged, 0 files removed, 0 files unresolved
$ hg diff
$ hg status
? file1.orig
$ hg id
08a16e8e4408 tip
$ hg update -C 0
1 files updated, 0 files merged, 0 files removed, 0 files unresolved
$ echo "changed file1" >> file1
$ hg update
1 files updated, 0 files merged, 0 files removed, 0 files unresolved
$ hg diff
$ hg status
? file1.orig
$ hg id
08a16e8e4408 tip
$ hg revert --all
$ hg diff
$ hg status
? file1.orig
$ hg id
08a16e8e4408 tip
$ hg revert -r tip --all
$ hg diff
$ hg status
? file1.orig
$ hg id
08a16e8e4408 tip
$ hg update -C
0 files updated, 0 files merged, 0 files removed, 0 files unresolved
$ hg diff
$ hg status
? file1.orig
$ hg id
08a16e8e4408 tip