extensions: list up only enabled extensions, if "ui" is specified
Before this patch, "extensions.extensions()" always lists up all
loaded extensions. So, commands handling multiple repositories at a
time like below enable extensions unexpectedly.
- clone from or push to localhost: extensions enabled only in the
source are enabled also in the destination
- pull from localhost: extensions enabled only in the destination
are enabled also in the source
- recursive execution in subrepo tree: extensions enabled only in
the parent or some of siblings in the tree are enabled also in
others
In addition to it, extensions disabled locally may be enabled
unexpectedly.
This patch checks whether each of extensions should be listed up or
not, if "ui" is specified to "extensions.extensions()", and invokes
"reposetup()" of each extensions only for repositories enabling it.