setdiscovery: use a revset for finding DAG heads in a subset
The march towards moving away from dagutil continues.
Like other patches moving us away from dagutil, there is the
potential for regressions to occur because revlogdag's
headsetofconnecteds() uses revlog.index, which doesn't take
filtering into account. The revset layer does. But no tests
fail, so we appear to be in the clear.
Differential Revision: https://phab.mercurial-scm.org/D4317
$ hg init
$ echo This is file a1 > a
$ hg add a
$ hg commit -m "commit #0"
$ echo This is file b1 > b
$ hg add b
$ hg commit -m "commit #1"
$ hg update 0
0 files updated, 0 files merged, 1 files removed, 0 files unresolved
$ echo This is file c1 > c
$ hg add c
$ hg commit -m "commit #2"
created new head
$ hg merge 1
1 files updated, 0 files merged, 0 files removed, 0 files unresolved
(branch merge, don't forget to commit)
$ rm b
$ echo This is file c22 > c
Test hg behaves when committing with a missing file added by a merge
$ hg commit -m "commit #3"
abort: cannot commit merge with missing files
[255]