push: add more output about what was added (issue #64)

l33t pointed out that currently, Hg-Git doesn't provide any confirmation that a
push was successful other than the exit code.  Normal Mercurial provides a
couple other messages followed by "added X changesets with Y changes to
Z files".  After this change, Hg-Git will provide much more similar output.
It's not identical, as the underlying model is substantially different, but the
concept is the same.  The main message is "added X commits with Y trees and
Z blobs".

This change doesn't affect the output of what references/branches were touched.
That will be addressed in a subsequent commit.

Dulwich doesn't provide an easy hook to get the information needed for this
output.  Instead of passing generate_pack_contents as the pack generator
function to send_pack, I pass a custom function that determines the "missing"
objects, stores the counts, and then calls generate_pack_contents (which then
will determine the "missing" objects again.

The new expected output:
searching for changes # unless quiet true
<N> commits found     # if verbose true
list of commits:      # if debugflag true and at least one commit found
<each hash>           # if debugflag true and at least one commit found
adding objects        # if at least one commit found unless quiet true
added <N> commits with <N> trees and <N> blobs # if at least one object unless
                                               # quiet true

https://bitbucket.org/durin42/hg-git/issue/64/push-confirmation
push: provide better output about changed references (issue #64)

As pointed out by l33t, Hg-Git's output for push doesn't currently do a very
good job of telling the user what happened.  My previous changes in this area
had moved some of the output from status to note, making it only show if
--verbose was specified.  However, I hadn't realized at the time that the
reference information (though overly verbose) was providing a valueable purpose
that otherwise wasn't met; telling the user that a remote reference had changed.

This changeset makes it so that:
*   default output will include simple messages like "adding reference
    refs/heads/feature" and "updating reference refs/heads/master" (omitting any
    mention of unchanged references)
*   verbose output will include more detailed messages like "adding reference
    default::refs/heads/feature => GIT:aba43c" and "updating reference
    default::refs/heads/master => GIT:aba43c" (omitting any mention of unchanged
    references)
*   debug output will include the detailed output like in verbose, but
    addtionally will include messages like "unchanged reference
    default::refs/heads/other => GIT:aba43c"

https://bitbucket.org/durin42/hg-git/issue/64/push-confirmation
scrub bad timezone values before dulwich sees them

If dulwich is presented with a "sub minute" timezone offset, it throws
an exception (see tests/test-timezone.t). This patch rounds the timezone
down to the next minute before passing the value to dulwich.

--HG--
extra : histedit_source : fa4c5b49e21e8e9550f9212d84b428b5f2e282ba
Add test to show dulwich fault on invalid timezone data

A recent real world occurrence - user hand edited the timezone field in
an hg export to provide a unique value (from prior export). Hg imported
the export okay, but dulwich threw an exception.

This test shows the fault.

--HG--
extra : histedit_source : 67c942f654d250cf28990ad117c1d0e8a18d498a