Re: Bizarre git merge behaviour

On 2013-11-20 08:20, Johannes Sixt wrote:
[...]

Not really. It's impossible to tell what's wrong if you

Hi Hannes,

Thanks for your response, and sorry for providing insufficient
information; this is a company Git repo (it's also about 200MB), so I've
got be careful what I post, but I can certainly give more than I've
shown already.

- show only ..topic
- but not topic..

I won't show the same (git log) output as I did previously, because
there are lots of commits and is a bit difficult to read (but can do so
as an attachment if you genuinely think it may be useful), but here's a
diff from wtf to merge-base:

mattcen@sonar:prisonpc(wtf)$ git --no-pager diff --numstat --oneline \
    "$(git merge-base wtf origin/22869-new-kernel)" wtf
1       1       .gitignore
1       1       bios-monitoring/bios-alert
4       4       bios-monitoring/check_bios.sh
1       7       bios-monitoring/ppc-bios.conf
3       0       client/scm/20-security.scm
14      0       client/scm/30-apps.scm
5       10      client/scm/30-branding.scm
2       7       client/scm/30-password-reset.scm
7       9       client/scm/50-kernel-prisoner.scm
7       9       client/scm/50-kernel-staff.scm
0       10      client/scm/50-prisoner.scm
4       1       client/transmute
2       1       client/transmute.scm.in
0       1       config-files-internet.txt
66      1       debian/NEWS
24      0       debian/changelog
6       3       debian/control
0       13      debian/postinst-cfg.sh
0       6       debian/prisonpc-core.config
8       5       debian/prisonpc-core.cron.d
12      6       debian/prisonpc-core.cron.daily
2       1       debian/prisonpc-core.install
35      94      debian/prisonpc-core.postinst
25      0       debian/prisonpc-core.ppcadm-yuk.init
0       4       debian/prisonpc-core.ppcadm.upstart
14      0       debian/prisonpc-core.preinst
27      0       debian/prisonpc-core.squid-yuk.init
0       11      debian/prisonpc-core.templates
16      2       debian/prisonpc-dev.cron.weekly
6       6       debian/prisonpc-dev.install
7       0       debian/prisonpc-dev.postinst
1       0       debian/prisonpc-internet.cron.daily
6       5       debian/prisonpc-internet.install
4       19      debian/prisonpc-internet.postinst
7       1       debian/rules
11      10      disc/disc_access
7       0       doc/Test_plan.txt
11      0       doc/Vectors.txt
-       -       doc/adminguide/images/streaming_media-screen.jpg
-       -       doc/adminguide/images/streaming_media-screen.png
-       -       doc/adminguide/images/web_filtering.png
8       17      doc/adminguide/streaming_media.rst
8       3       doc/adminguide/system-status.rst
13      16      doc/adminguide/web_filtering.rst
127     0       doc/current-mail-status.txt
55      0       doc/prisonpc-mail-plan.dot
90      0       doc/prisonpc-mail.dot
2       0       doc/user_acceptance_tests/.gitignore
22      0       doc/user_acceptance_tests/README
581     0       doc/user_acceptance_tests/default.css
1011    0       doc/user_acceptance_tests/user_acceptance_tests.rst
2       2       dovecot/dovecot-staff.conf
0       579     dovecot/email_quarantine
8       5       eric/apps/complain.py
5       3       eric/apps/links.py
7       3       eric/apps/media.py
5       3       eric/apps/whitelist.py
4       0       eric/eric
1       0       eric/eric_cfg.py
48      0       generate-mail-stats
12      2       post-install.sh
10      0       postfix/alias-list
2       0       postfix/by-week.procmailrc
0       11      postfix/flush-queued-mail
2       0       postfix/invariant.procmailrc
49      67      postfix/main.cf.in
3       36      postfix/master-basic.cf.in
51      144     postfix/master-filter.cf.in
145     156     postfix/maxwell
0       15      postfix/maxwell.cfg.in
31      0       postfix/maybe
76      0       postfix/plainify
0       0       postfix/plainify.d/cur/00-nothing
6       0       postfix/plainify.d/cur/01-nonmime
12      0       postfix/plainify.d/cur/02-th
8       0       postfix/plainify.d/cur/02-tp
35761   0       postfix/plainify.d/cur/f0-many-types
832     0       postfix/plainify.d/cur/f0-rfc822
244     0       postfix/plainify.d/cur/f0-th_tbird_cascade
0       167     postfix/smtp_archiver
0       240     postfix/strip_quarantine_markers
119     248     postfix/whitelist
85      37      ppcadm/modules/disc_access.py
80      0       ppcadm/modules/emailstats.py
8       7       ppcadm/modules/mailfilter.py
130     49      ppcadm/modules/media.py
58      74      ppcadm/modules/quarantine.py
87      37      ppcadm/modules/wwwfilter.py
3       0       ppcadm/resources/admin.css
31      0       ppcadm/templates/disc_access.tpl
5       0       ppcadm/templates/disc_summary.tpl
7       6       ppcadm/templates/home.tpl
2       2       ppcadm/templates/mailfilter_menu.tpl
1       2       ppcadm/templates/quarantine_list.tpl
33      17      ppcadm/templates/quarantine_mail.tpl
67      0       ppcadm/templates/streaming_media.tpl
3       3       ppcadm/templates/user.tpl
100     0       ppcadm/templates/wwwfilter.tpl
36      27      pre-install.sh
17      21      squid/check_greylist
2       1       squid/make_url_regex
8       34      squid/remove_user.sh
8       24      squid/update_user.sh
7       16      squid/validate_url_comment
2       1       streaming-media/autodvdencode
2       1       streaming-media/m3u-slurp
4       4       streaming-media/media-stream
2       1       streaming-media/vobcopy_wrapper
2       1       switch/switch-cmd
23      1       tca/parts.d/pxelinux-cfg
14      6       tca/rebuild_prisoner_realm_access
7       4       tca/rebuild_prisoner_realm_service_access
48      147     tca/tca.pm
18      10      tca/tca_realm_access
6       5       tca/tca_realm_service_access
0       9       trimserver/trimserver.cfg.in
14      43      trimserver/trimserver.pm
0       42      webmin/rcs_ci
6       0       webmin/reset_user_desktop_config
10      49      webmin/sort_ci
1       4       webmin/sort_ci.8
0       12      webmin/sort_ci_correct
11      14      webmin/whitelist_update

- and you keep secret which of the changes is unexpected.

The only changes I expect are these:

mattcen@sonar:prisonpc(wtf)$ git --no-pager diff --numstat --oneline \
    "$(git merge-base wtf origin/22869-new-kernel)" origin/22869-new-kernel
37      0       client/kernel/README
2797    0       client/kernel/config-3.5.7.20-1
0       3525    client/kernel/config-3.5.7.21-1
-       -       client/kernel/linux-firmware-image_3.5.7.21-1_i386.deb
-       -       client/kernel/linux-image-3.5.7.20_3.5.7.20-1_i386.deb
-       -       client/kernel/linux-image-3.5.7.21_3.5.7.21-1_i386.deb
1       0       client/scm/20-security.scm
6       7       client/scm/50-kernel-prisoner.scm
1       0       client/scm/50-staff.scm
22      0       doc/user_acceptance_tests/README
581     0       doc/user_acceptance_tests/default.css
1548    0       doc/user_acceptance_tests/user_acceptance_tests.html
4268    0       doc/user_acceptance_tests/user_acceptance_tests.pdf
940     0       doc/user_acceptance_tests/user_acceptance_tests.rst

Perhaps you did the following:

- On one branch, you made a change A and then another change B that reverts A.
- On the other branch, you also made the same changes as A, but there is
no equivalent of B.

In this case, it is expected that the changes made by B (i.e. the reversal
of change A) are *NOT* in the merge, i.e., the changes of A survive. It
looks as if the merge reverted change B.

I have found no evidence that this happened, but am not confident enough
to rule it out.

If that is not the case, it could be helpful that you pick one of the
files that contains an unexpected change and post the output of

git log --left-right --oneline wtf...origin/22869-new-kernel \
    file/with/changes | cut -c1-70

Sure. I don't expect the merge to cause any changes to quarantine.py:

mattcen@sonar:prisonpc(wtf)$ git log --left-right --oneline \
    wtf...origin/22869-new-kernel ppcadm/modules/quarantine.py | cut -c1-70
< 5b5f552 Fixed msg vs msg.as_string because smtp.sendmail is picky
< 03618f2 Use Return-Path, not X-Original-Envelope-From.
< dc1169e Bug squashing.
< 8e20216 Changed quarantine module to run maybe and send directly to
< d79ad42 Change final port, name the magic number.
< e44d1b3 Merge remote-tracking branch 'origin/staging' into 22912-ppc
< a03db6d Modified quarantine UI to handle the new reports format

Further, there are other files that don't change at all on either side
of the symetric diff:

mattcen@sonar:prisonpc(wtf)$ git log -M -C  --left-right --oneline \
    wtf...origin/22869-new-kernel generate-mail-stats | cut -c1-70
<no output>

I'm truly stumped. It's also worth noting that I've gone through and
manually resolved this merge one file at a time, and I'm about 90% sure
I ended up with the correct result, but it'd be nice to have had the
merge do the right thing in the first place, and I obviously want to
avoid having to do this again in a few months' time.

-- 
Regards,
Matthew Cengia