repair: setup hookargs when processing bundle2s

addchangegroup() modifies its behavior based on the transaction source.
This is incorrect for bundle2 repair files, causing rebases to abort when this
option is enabled.

This diff specifies the source type in the way recommended by comments in
bundle2.py and adds a test to ensure that rebases with the experimental option
work successfully.

mercurial/repair.py

@@ -181,6 +181,8 b' def strip(ui, repo, nodelist, backup=Tru'
                 repo.ui.pushbuffer()
             if isinstance(gen, bundle2.unbundle20):
                 tr = repo.transaction('strip')
+                tr.hookargs = {'source': 'strip',
+                               'url': 'bundle:' + vfs.join(chgrpfile)}
                 try:
                     bundle2.processbundle(repo, gen, lambda: tr)
                     tr.close()

tests/test-rebase-pull.t

@@ -165,5 +165,47 b' pull --rebase works when a specific revi'
   |
   o  0: 'C1'
   
+pull --rebase works with bundle2 turned on
 
-
+  $ cd ../a
+  $ echo R4 > R4
+  $ hg ci -Am R4
+  adding R4
+  $ hg tglog
+  @  5: 'R4'
+  |
+  o  4: 'R3'
+  |
+  o  3: 'R2'
+  |
+  o  2: 'R1'
+  |
+  o  1: 'C2'
+  |
+  o  0: 'C1'
+  
+  $ cd ../c
+  $ hg pull --rebase --config experimental.bundle2-exp=True --config experimental.strip-bundle2-version=02
+  pulling from $TESTTMP/a (glob)
+  searching for changes
+  adding changesets
+  adding manifests
+  adding file changes
+  added 1 changesets with 1 changes to 1 files (+1 heads)
+  rebasing 5:518d153c0ba3 "L1"
+  saved backup bundle to $TESTTMP/c/.hg/strip-backup/518d153c0ba3-73407f14-backup.hg (glob)
+  $ hg tglog
+  @  6: 'L1'
+  |
+  o  5: 'R4'
+  |
+  o  4: 'R3'
+  |
+  o  3: 'R2'
+  |
+  o  2: 'R1'
+  |
+  o  1: 'C2'
+  |
+  o  0: 'C1'
+