exchange: support sorting URLs by client-side preferences
Not all bundles are appropriate for all clients. For example, someone
with a slow Internet connection may want to prefer bz2 bundles over gzip
bundles because they are smaller and don't take as long to transfer.
This is information that a server cannot know on its own. So, we invent
a mechanism for "preferring" server-advertised URLs based on their
attributes.
We could invent a negotiation between client and server where the client
sends its preferences and the sorting/filtering is done server-side.
However, this feels complex. We can avoid complicating the wire protocol
and exposing ourselves to backwards compatible concerns by performing
the sorting locally.
This patch defines a new config option for expressing preferred
attributes in server-advertised bundles.
At Mozilla, we leverage this feature so clients in fast data centers
prefer uncompressed bundles. (We advertise gzip bundles first because
that is a reasonable default.)
I consider this an advanced feature. I'm on the fence as to whether it
should be documented in `hg help config`.
#!/usr/bin/python
from mercurial.ui import ui
from mercurial.localrepo import localrepository
from mercurial.commands import add, commit, status
u = ui()
print '% creating repo'
repo = localrepository(u, '.', create=True)
f = open('test.py', 'w')
try:
f.write('foo\n')
finally:
f.close
print '% add and commit'
add(u, repo, 'test.py')
commit(u, repo, message='*')
status(u, repo, clean=True)
print '% change'
f = open('test.py', 'w')
try:
f.write('bar\n')
finally:
f.close()
# this would return clean instead of changed before the fix
status(u, repo, clean=True, modified=True)