evolve: refactor content-divergence resolution logic > What is the case we are looking at? This is about refactoring the part of content-div resolution logic where it decides which cset should be relocated and where. > What is a "topologicial common ancestors" vs a "greatest common ancestors"? `tca` is an ancestor which we can decide/find by looking at the at graph visually for e.g ``` c3(*) c4(*) | | c2(x) c1(x) c5 | / \ | / c0 ``` (c5 is the successor of c2 and c1) now here, `tca` of c3 and c4 is: c0 `gca` of c3 and c4 is: c5 > What is the new top-level logic/behavior that makes it better? The old code had some unnecessary edge cases just because we were using `gca`, since it can point to a revision that is not a topological ancestor. For e.g see b779b40f996e Eventually, the code around this was getting messy unnecessarily. So I looked into it and found a simple and more robust approach. And in new code, it is simple and straightforward (and easy to understand), where we handle the following 4 cases when solving content-div: 1) when both are on the same parent => (no need to do anything special, and simply proceed) 2) both are on the different parent but a) `tca` is the parent of one of them or b) there is no non-obsolete revision between `tca` and one of the divergent cset. => (relocate one to the other side and proceed) 3) both are on different parents and `tca` is not the parent of any of them and there is at least one non-obsolete cset between tca and both the divergent cset i.e (tca::div1) and (tca::div2) both the ranges have at least one non-obs revision. => (this is the case which we don't handle yet, but the solution would be to prompt the user to choose an evolve destination.) 4) both are in the parent-child relation => (both are merged and new cset will be based on the successor of `tca`) Changes in test-evolve-issue5958.t demonstrate that new code also covered case4 because in a resolution of "two divergent csets with parent-child relation" there should be one cset as a result and no orphan revs (as you can see there was an orphan before this patch).

Testing topics on cases when we have multiple topics based on top
of other.
  $ . "$TESTDIR/testlib/topic_setup.sh"

Setup

  $ cat << EOF >> $HGRCPATH
  > [experimental]
  > evolution = all
  > [ui]
  > interactive = True
  > logtemplate = {rev} - \{{get(namespaces, "topics")}} {node|short} {desc} ({phase})\n
  > [extensions]
  > show =
  > EOF
  $ echo "evolve=$(echo $(dirname $TESTDIR))/hgext3rd/evolve/" >> $HGRCPATH

Test to make sure `hg evolve` don't solve troubles out of current stack:
------------------------------------------------------------------------

  $ hg init repo1
  $ cd repo1
  $ for ch in a b c; do
  > echo $ch > $ch
  > hg ci -Am "added "$ch --topic foo
  > done;
  adding a
  active topic 'foo' grew its first changeset
  (see 'hg help topics' for more information)
  adding b
  adding c

  $ echo d > d
  $ hg ci -Am "added d" --topic bar
  adding d
  active topic 'bar' grew its first changeset
  (see 'hg help topics' for more information)

  $ hg up -r "desc('added c')"
  > echo cc >> c
  switching to topic foo
  0 files updated, 0 files merged, 1 files removed, 0 files unresolved
  $ hg amend
  1 new orphan changesets

  $ hg log -G
  @  4 - {foo} 0cc68cbf943a added c (draft)
  |
  | *  3 - {bar} 94b12ff0f44a added d (draft)
  | |
  | x  2 - {foo} 9c315cf1e7de added c (draft)
  |/
  o  1 - {foo} ead01932caf0 added b (draft)
  |
  o  0 - {foo} 853c9ec0849e added a (draft)
  

  $ hg stack
  ### topic: foo
  ### target: default (branch)
  s3@ added c (current)
  s2: added b
  s1: added a

As expected, evolve should deny to evolve here as there is no troubled csets in current stack:
  $ hg evolve --all
  nothing to evolve on current working copy parent
  (1 other orphan in the repository, do you want --any or --rev)
  [2]