view tests/test-issue2137.t @ 38486:4c0683655599

namespaces: let namespaces override singlenode() definition

Some namespaces have multiple nodes per name (meaning that their
namemap() returns multiple nodes). One such namespace is the "topics"
namespace (from the evolve repo). We also have our own internal
namespace at Google (for review units) that has multiple nodes per
name. These namespaces may not want to use the default "pick highest
revnum" resolution that we currently use when resolving a name to a
single node. As an example, they may decide that `hg co <name>` should
check out a commit that's last in some sense even if an earlier commit
had just been amended and thus had a higher revnum [1]. This patch
gives the namespace the option to continue to return multiple nodes
and to override how the best node is picked. Allowing namespaces to
override that may also be useful as an optimization (it may be cheaper
for the namespace to find just that node).

I have been arguing (in D3715) for using all the nodes returned from
namemap() when resolving the symbol to a revset, so e.g. `hg log -r
stable` would resolve to *all* nodes on stable, not just the one with
the highest revnum (except that I don't actually think we should
change it for the branch namespace because of BC). Most people seem
opposed to that. If we decide not to do it, I think we can deprecate
the namemap() function in favor of the new singlenode() (I find it
weird to have namespaces, like the branch namespace, where namemap()
isn't nodemap()'s inverse). I therefore think this patch makes sense
regardless of what we decide on that issue.


 [1] Actually, even the branch namespace would have wanted to override
     singlenode() if it had supported multiple nodes. That's because
     closes branch heads are mostly ignored, so "hg co default" will
     not check out the highest-revnum node if that's a closed head.

Differential Revision: https://phab.mercurial-scm.org/D3852

https://bz.mercurial-scm.org/2137

Setup:

create a little extension that has 3 side-effects:
1) ensure changelog data is not inlined
2) make revlog to use lazyparser
3) test that repo.lookup() works
1 and 2 are preconditions for the bug; 3 is the bug.

  $ cat > commitwrapper.py <<EOF
  > from mercurial import extensions, node, revlog
  > 
  > def reposetup(ui, repo):
  >     class wraprepo(repo.__class__):
  >         def commit(self, *args, **kwargs):
  >             result = super(wraprepo, self).commit(*args, **kwargs)
  >             tip1 = node.short(repo.changelog.tip())
  >             tip2 = node.short(repo.lookup(tip1))
  >             assert tip1 == tip2
  >             ui.write(b'new tip: %s\n' % tip1)
  >             return result
  >     repo.__class__ = wraprepo
  > 
  > def extsetup(ui):
  >     revlog._maxinline = 8             # split out 00changelog.d early
  >     revlog._prereadsize = 8           # use revlog.lazyparser
  > EOF

  $ cat >> $HGRCPATH <<EOF
  > [extensions]
  > commitwrapper = `pwd`/commitwrapper.py
  > EOF

  $ hg init repo1
  $ cd repo1
  $ echo a > a
  $ hg commit -A -m'add a with a long commit message to make the changelog a bit bigger'
  adding a
  new tip: 553596fad57b

Test that new changesets are visible to repo.lookup():

  $ echo a >> a
  $ hg commit -m'one more commit to demonstrate the bug'
  new tip: 799ae3599e0e

  $ hg tip
  changeset:   1:799ae3599e0e
  tag:         tip
  user:        test
  date:        Thu Jan 01 00:00:00 1970 +0000
  summary:     one more commit to demonstrate the bug
  

  $ cd ..