namespaces: generate template keyword when registering a namespace
For any namespace, we generate a template keyword. For example, given a
namespace 'babar', we automatically have the ability to use it in a template:
hg log -r . -T '{babars % "King: {babar}\n"}'
Furthermore, we only generate this keyword for a namespace if one doesn't
already exist. This is necessary for 'branches' and 'bookmarks' since both of
those have concepts of 'current' (something outside the namespace api) and also
allows extensions to override default behavior if desired.
$ echo 'raise Exception("bit bucket overflow")' > badext.py
$ abspath=`pwd`/badext.py
$ cat <<EOF >> $HGRCPATH
> [extensions]
> gpg =
> hgext.gpg =
> badext = $abspath
> badext2 =
> EOF
$ hg -q help help
*** failed to import extension badext from $TESTTMP/badext.py: bit bucket overflow
*** failed to import extension badext2: No module named badext2
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