copies: expand `_chain` variable name to make the function easier to read This came up while explaining what the function is about. I find the function easier to follow that way.

copies: show we can read data from the "first" mapping In practice this make no difference since `t` is a copy of `a`. Having this change before hand will make the next cleanup changeset clearer. This is work on the road to using some native code for some performance critical part of copy tracing.

copies: return consistent type from revinfo The return is expected to be a list, so we should return a list. This make the use of this function from type-checked language (eg: rust) much simpler.

dateutil: correct default for Ymd in parsedate The code uses `0` for the default value of Ymd (year, month, and day), which seems suboptimal. For example, these will fail to parse: dateutil.parsedate('2000', formats=dateutil.extendeddateformats) dateutil.parsedate('Jan 2000', formats=dateutil.extendeddateformats) Fix it by providing sane defaults (1 instead of 0) for year, month, and day. The suboptimal behavior was introduced by 91bc001a592 (2010-12-29, "date: fix matching of underspecified date ranges"), which does not seem to justify the current behavior. Note end-users should not notice the subtle issue, because there are no formats in `defaultdateformats` that allow an explicit year with omitted month, or an explicit month with omitted day. Differential Revision: https://phab.mercurial-scm.org/D7520

test-doctest: include dateutil `mercurial.utils.dateutil` has dostrings that contain doctests. Include them. Differential Revision: https://phab.mercurial-scm.org/D7519

revlog: fix revset in reachableroots docstring `reachableroots` will only return a subset of `roots` when `includepath` is False. For example, given the following linear DAG: 2 | 1 | 0 Using roots=0+2, heads=1, the definition in the docstring does not match what `reachableroots` actually does: ipdb> repo.changelog.reachableroots(0, roots=[0,2],heads=[1]) [0] ipdb> repo.revs('heads(::(0+2) & (0+2)::1)') <baseset+ [1]> The fix is to do `heads & ::roots` (or `heads & heads::roots`) first, then select their ancestors: ipdb> repo.revs('heads(::((0+2) & (0+2)::1))') <baseset+ [0]> The docstring was introduced by fd92bfbbe02d9 (2015-06-19 "revset: rename revsbetween to reachableroots and add an argument"), which introduced the `includepath=False` behavior for graphlog grandparents use-case. I believe the docstring instead of the code should be changed because changing the code to match the docstring can result in suboptimal graphlog like: o :\ : o : : :/ o As opposite to the current "linearized" graphlog: o | o : o Differential Revision: https://phab.mercurial-scm.org/D7518