unionrepo: read-only operations on a union of two localrepos unionrepo is just like bundlerepo without bundles. The implementation is very similar to bundlerepo, but I don't see any obvious way to generalize it. Some most obvious use cases for this would be log and diff across local repos, as a kind of preview of pulls, for instance: $ hg -R union:repo1+repo2 heads $ hg -R union:repo1+repo2 log -r REPO1REV -r REPO2REV $ hg -R union:repo1+repo2 log -r '::REPO1REV-::REPO2REV' $ hg -R union:repo1+repo2 log -r 'ancestor(REPO1REV,REPO2REV)' $ hg -R union:repo1+repo2 diff -r REPO1REV -r REPO2REV This is going to be used in RhodeCode, and Bitbucket already uses something similar. Having a core implementation would be beneficial.

--- a/mercurial/hg.py	Mon Apr 15 23:52:57 2013 +0900
+++ b/mercurial/hg.py	Fri Jan 18 15:54:09 2013 +0100
@@ -9,8 +9,8 @@
 from i18n import _
 from lock import release
 from node import hex, nullid
-import localrepo, bundlerepo, httppeer, sshpeer, statichttprepo, bookmarks
-import lock, util, extensions, error, node, scmutil, phases, url
+import localrepo, bundlerepo, unionrepo, httppeer, sshpeer, statichttprepo
+import bookmarks, lock, util, extensions, error, node, scmutil, phases, url
 import cmdutil, discovery
 import merge as mergemod
 import verify as verifymod
@@ -64,6 +64,7 @@
 
 schemes = {
     'bundle': bundlerepo,
+    'union': unionrepo,
     'file': _local,
     'http': httppeer,
     'https': httppeer,