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`.
$ hg init
$ echo "added file1" > file1
$ echo "another line of text" >> file1
$ echo "added file2" > file2
$ hg add file1 file2
$ hg commit -m "added file1 and file2"
$ echo "changed file1" >> file1
$ hg commit -m "changed file1"
$ hg -q log
1:dfab7f3c2efb
0:c3fa057dd86f
$ hg id
dfab7f3c2efb tip
$ hg update -C 0
1 files updated, 0 files merged, 0 files removed, 0 files unresolved
$ hg id
c3fa057dd86f
$ echo "changed file1" >> file1
$ hg id
c3fa057dd86f+
$ hg revert --no-backup --all
reverting file1
$ hg diff
$ hg status
$ hg id
c3fa057dd86f
$ hg update
1 files updated, 0 files merged, 0 files removed, 0 files unresolved
$ hg diff
$ hg status
$ hg id
dfab7f3c2efb tip
$ hg update -C 0
1 files updated, 0 files merged, 0 files removed, 0 files unresolved
$ echo "changed file1 different" >> file1
$ hg update
merging file1
warning: conflicts while merging file1! (edit, then use 'hg resolve --mark')
0 files updated, 0 files merged, 0 files removed, 1 files unresolved
use 'hg resolve' to retry unresolved file merges
[1]
$ hg diff --nodates
diff -r dfab7f3c2efb file1
--- a/file1
+++ b/file1
@@ -1,3 +1,7 @@
added file1
another line of text
+<<<<<<< working copy: c3fa057dd86f - test: added file1 and file2
+changed file1 different
+=======
changed file1
+>>>>>>> destination: dfab7f3c2efb - test: changed file1
$ hg status
M file1
? file1.orig
$ hg id
dfab7f3c2efb+ tip
$ hg revert --no-backup --all
reverting file1
$ hg diff
$ hg status
? file1.orig
$ hg id
dfab7f3c2efb tip
$ hg revert -r tip --no-backup --all
$ hg diff
$ hg status
? file1.orig
$ hg id
dfab7f3c2efb tip
$ hg update -C
0 files updated, 0 files merged, 0 files removed, 0 files unresolved
$ hg diff
$ hg status
? file1.orig
$ hg id
dfab7f3c2efb tip