Excess data size for a single revision

[Eli Zaretskii]

This happened lately with the trunk of the Emacs repository: updating
the local branch for revision 106891 pulls 58MB of data through the
wire:

  [18725] 2012-01-19 06:35:06.319 INFO: Updated to revision 106892 of branch bzr+ssh://eliz@bzr.savannah.gnu.org/emacs/trunk
  50.898  Transferred: 58583kB (1242.3kB/s r:58577kB w:6kB)

(The previous revision I had was 106888, so 106891 actually pulls a
little less than 58MB.)

I saw this consistently on 2 different machines, one running
GNU/Linux, the other running MS-Windows.

The only thing that is special about revision 106891 is that it merged
26 revisions from the emacs-23 branch.  "bzr st" says that this merge
modified just 7 files, and "bzr diff" says the changes are about 200
lines, including context lines.  So I'm guessing most of the data
pulled is meta-data.

But why would a single merge result in so much meta-data?