templatekw: make {latesttag} a hybrid list
This maintains the previous behavior of expanding {latesttag} to a string
containing all of the tags, joined by ':'. But now it also allows list type
operations.
I'm unsure if the plural handling is correct (i.e. it seems like it is usually
"{foos % '{foo}'}"), but I guess we are stuck with this because the singular
form previously existed.
http://mercurial.selenic.com/bts/issue1089
$ hg init
$ mkdir a
$ echo a > a/b
$ hg ci -Am m
adding a/b
$ hg rm a
removing a/b (glob)
$ hg ci -m m a
$ mkdir a b
$ echo a > a/b
$ hg ci -Am m
adding a/b
$ hg rm a
removing a/b (glob)
$ cd b
Relative delete:
$ hg ci -m m ../a
$ cd ..