Move cmdtable and reposetup handling out of extensions.py
A new function (extensions.extensions) allows the code that is
interested in those attributes to handle them directly.
This allows some cleanups of extensions.py. Notably, we can
remove the extensions.commandtable hack.
It also makes it easier to add standard extension attributes,
like a "hgwebsetup" function or a "helptable" dict that augments
the data in help.py, etc.
#!/bin/sh
hg init repo
cd repo
echo line 1 > foo
hg ci -qAm 'add foo' -d "1000000 0"
# copy foo to bar and change both files
hg cp foo bar
echo line 2-1 >> foo
echo line 2-2 >> bar
hg ci -m 'cp foo bar; change both' -d "1000000 0"
# in another branch, change foo in a way that doesn't conflict with
# the other changes
hg up -qC 0
echo line 0 > foo
hg cat foo >> foo
hg ci -m 'change foo' -d "1000000 0"
# we get conflicts that shouldn't be there
hg merge --debug
echo "-- foo --"
cat foo
echo "-- bar --"
cat bar