R1:81dcf6378d81

Make `repository pull` install hooks the first time

Summary:
Ref T4257. Currently, the pull logic looks like this:

if (new) {
create();
} else {
if (hosted) {
install_hooks();
} else {
update();
}
}

This means that the first time you run `repository pull`, hooks aren't installed, which makes debugging trickier. Instead, reorganize the logic:

if (new) {
create();
} else {
if (!hosted) {
update();
}
}

if (hosted) {
install_hooks();
}…