rebase: calculate ancestors for --base separately (issue5420)
Previously, the --base option only works with a single "branch" - if there
is one changeset in the "--base" revset whose branching point(s) is/are
different from another changeset in the "--base" revset, "rebase" will error
out with:
abort: source is ancestor of destination
This happens if the user has multiple draft branches, and uses "hg rebase -b
'draft()' -d master", for example. The error message looks cryptic to users
who don't know the implementation detail.
This patch changes the logic to calculate the common ancestor for every
"base" changeset separately so we won't (incorrectly) select "source" which
is an ancestor of the destination.
This patch should not change the behavior where all changesets specified by
"--base" have the same branching point(s).
A new situation is: some of the specified changesets could be rebased, while
some couldn't (because they are descendants of the destination, or they do
not share a common ancestor with the destination). The current behavior is
to show "nothing to rebase" and exits with 1.
This patch maintains the current behavior (show "nothing to rebase") even if
part of the "--base" revset could be rebased. A clearer error message may be
"cannot find branching point for X", or "X is a descendant of destination".
The error message issue is tracked by issue5422 separately.
A test is added with all kinds of tricky cases I could think of for now.
# The test-repo is a live hg repository which may have evolution
# markers created, e.g. when a ~/.hgrc enabled evolution.
#
# Tests are run using a custom HGRCPATH, which do not
# enable evolution markers by default.
#
# If test-repo includes evolution markers, and we do not
# enable evolution markers, hg will occasionally complain
# when it notices them, which disrupts tests resulting in
# sporadic failures.
#
# Since we aren't performing any write operations on the
# test-repo, there's no harm in telling hg that we support
# evolution markers, which is what the following lines
# for the hgrc file do:
cat >> $HGRCPATH << EOF
[experimental]
evolution=createmarkers
EOF