namespaces: add nodemap property
This patch adds a node-to-name map property to the namespace. This is necessary
because we cannot simply invert the name-to-node map because we do not assume
the name-to-node map to be unique (for example, consider named branches: many
nodes have one branch name).
The node-to-name is helpful in log commands where we are already iterating over
a set of nodes and want to display some kind of naming information to the user.
http://mercurial.selenic.com/bts/issue619
$ hg init
$ echo a > a
$ hg ci -Ama
adding a
$ echo b > b
$ hg branch b
marked working directory as branch b
(branches are permanent and global, did you want a bookmark?)
$ hg ci -Amb
adding b
$ hg co -C 0
0 files updated, 0 files merged, 1 files removed, 0 files unresolved
Fast-forward:
$ hg merge b
1 files updated, 0 files merged, 0 files removed, 0 files unresolved
(branch merge, don't forget to commit)
$ hg ci -Ammerge
Bogus fast-forward should fail:
$ hg merge b
abort: merging with a working directory ancestor has no effect
[255]
Even with strange revset (issue4465)
$ hg merge ::.
abort: merging with a working directory ancestor has no effect
[255]