tags: return tags in sorted order
This makes log and summary have less arbitrary tag ordering and also
groups similar tags together, such as the mq tags.
# -- setting up base repo
adding a
# -- cloning base repo
updating to branch default
1 files updated, 0 files merged, 0 files removed, 0 files unresolved
# -- setting up cset to push
0 files updated, 0 files merged, 1 files removed, 0 files unresolved
adding a
created new head
# -- pushing
pushing to ../a
searching for changes
adding changesets
adding manifests
adding file changes
added 1 changesets with 0 changes to 0 files (+1 heads)