view tests/test-empty-group.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

#  A          B
#
#  3  4       3
#  |\/|       |\
#  |/\|       | \
#  1  2       1  2
#  \ /        \ /
#   0          0
#
# if the result of the merge of 1 and 2
# is the same in 3 and 4, no new manifest
# will be created and the manifest group
# will be empty during the pull
#
# (plus we test a failure where outgoing
# wrongly reported the number of csets)

  $ hg init a
  $ cd a
  $ touch init
  $ hg ci -A -m 0
  adding init
  $ touch x y
  $ hg ci -A -m 1
  adding x
  adding y

  $ hg update 0
  0 files updated, 0 files merged, 2 files removed, 0 files unresolved
  $ touch x y
  $ hg ci -A -m 2
  adding x
  adding y
  created new head

  $ hg merge 1
  0 files updated, 0 files merged, 0 files removed, 0 files unresolved
  (branch merge, don't forget to commit)
  $ hg ci -A -m m1

  $ hg update -C 1
  0 files updated, 0 files merged, 0 files removed, 0 files unresolved
  $ hg merge 2
  0 files updated, 0 files merged, 0 files removed, 0 files unresolved
  (branch merge, don't forget to commit)
  $ hg ci -A -m m2
  created new head

  $ cd ..

  $ hg clone -r 3 a b
  adding changesets
  adding manifests
  adding file changes
  added 4 changesets with 3 changes to 3 files
  new changesets 5fcb73622933:d15a0c284984
  updating to branch default
  3 files updated, 0 files merged, 0 files removed, 0 files unresolved

  $ hg clone -r 4 a c
  adding changesets
  adding manifests
  adding file changes
  added 4 changesets with 3 changes to 3 files
  new changesets 5fcb73622933:1ec3c74fc0e0
  updating to branch default
  3 files updated, 0 files merged, 0 files removed, 0 files unresolved

  $ hg -R a outgoing b
  comparing with b
  searching for changes
  changeset:   4:1ec3c74fc0e0
  tag:         tip
  parent:      1:79f9e10cd04e
  parent:      2:8e1bb01c1a24
  user:        test
  date:        Thu Jan 01 00:00:00 1970 +0000
  summary:     m2
  
  $ hg -R a outgoing c
  comparing with c
  searching for changes
  changeset:   3:d15a0c284984
  parent:      2:8e1bb01c1a24
  parent:      1:79f9e10cd04e
  user:        test
  date:        Thu Jan 01 00:00:00 1970 +0000
  summary:     m1
  
  $ hg -R b outgoing c
  comparing with c
  searching for changes
  changeset:   3:d15a0c284984
  tag:         tip
  parent:      2:8e1bb01c1a24
  parent:      1:79f9e10cd04e
  user:        test
  date:        Thu Jan 01 00:00:00 1970 +0000
  summary:     m1
  
  $ hg -R c outgoing b
  comparing with b
  searching for changes
  changeset:   3:1ec3c74fc0e0
  tag:         tip
  parent:      1:79f9e10cd04e
  parent:      2:8e1bb01c1a24
  user:        test
  date:        Thu Jan 01 00:00:00 1970 +0000
  summary:     m2
  

  $ hg -R b pull a
  pulling from a
  searching for changes
  adding changesets
  adding manifests
  adding file changes
  added 1 changesets with 0 changes to 0 files (+1 heads)
  new changesets 1ec3c74fc0e0
  (run 'hg heads' to see heads, 'hg merge' to merge)

  $ hg -R c pull a
  pulling from a
  searching for changes
  adding changesets
  adding manifests
  adding file changes
  added 1 changesets with 0 changes to 0 files (+1 heads)
  new changesets d15a0c284984
  (run 'hg heads' to see heads, 'hg merge' to merge)