annotate tests/test-notify.t @ 30155:b7a966ce89ed

changelog: disable delta chains

This patch disables delta chains on changelogs. After this patch, new
entries on changelogs - including existing changelogs - will be stored
as the fulltext of that data (likely compressed). No delta computation
will be performed.

An overview of delta chains and data justifying this change follows.

Revlogs try to store entries as a delta against a previous entry (either
a parent revision in the case of generaldelta or the previous physical
revision when not using generaldelta). Most of the time this is the
correct thing to do: it frequently results in less CPU usage and smaller
storage.

Delta chains are most effective when the base revision being deltad
against is similar to the current data. This tends to occur naturally
for manifests and file data, since only small parts of each tend to
change with each revision. Changelogs, however, are a different story.

Changelog entries represent changesets/commits. And unless commits in a
repository are homogonous (same author, changing same files, similar
commit messages, etc), a delta from one entry to the next tends to be
relatively large compared to the size of the entry. This means that
delta chains tend to be short. How short? Here is the full vs delta
revision breakdown on some real world repos:

Repo             % Full    % Delta   Max Length
hg                45.8       54.2        6
mozilla-central   42.4       57.6        8
mozilla-unified   42.5       57.5       17
pypy              46.1       53.9        6
python-zstandard  46.1       53.9        3

(I threw in python-zstandard as an example of a repo that is homogonous.
It contains a small Python project with changes all from the same
author.)

Contrast this with the manifest revlog for these repos, where 99+% of
revisions are deltas and delta chains run into the thousands.

So delta chains aren't as useful on changelogs. But even a short delta
chain may provide benefits. Let's measure that.

Delta chains may require less CPU to read revisions if the CPU time
spent reading smaller deltas is less than the CPU time used to
decompress larger individual entries. We can measure this via
`hg perfrevlog -c -d 1` to iterate a revlog to resolve each revision's
fulltext. Here are the results of that command on a repo using delta
chains in its changelog and on a repo without delta chains:

hg (forward)
! wall 0.407008 comb 0.410000 user 0.410000 sys 0.000000 (best of 25)
! wall 0.390061 comb 0.390000 user 0.390000 sys 0.000000 (best of 26)

hg (reverse)
! wall 0.515221 comb 0.520000 user 0.520000 sys 0.000000 (best of 19)
! wall 0.400018 comb 0.400000 user 0.390000 sys 0.010000 (best of 25)

mozilla-central (forward)
! wall 4.508296 comb 4.490000 user 4.490000 sys 0.000000 (best of 3)
! wall 4.370222 comb 4.370000 user 4.350000 sys 0.020000 (best of 3)

mozilla-central (reverse)
! wall 5.758995 comb 5.760000 user 5.720000 sys 0.040000 (best of 3)
! wall 4.346503 comb 4.340000 user 4.320000 sys 0.020000 (best of 3)

mozilla-unified (forward)
! wall 4.957088 comb 4.950000 user 4.940000 sys 0.010000 (best of 3)
! wall 4.660528 comb 4.650000 user 4.630000 sys 0.020000 (best of 3)

mozilla-unified (reverse)
! wall 6.119827 comb 6.110000 user 6.090000 sys 0.020000 (best of 3)
! wall 4.675136 comb 4.670000 user 4.670000 sys 0.000000 (best of 3)

pypy (forward)
! wall 1.231122 comb 1.240000 user 1.230000 sys 0.010000 (best of 8)
! wall 1.164896 comb 1.160000 user 1.160000 sys 0.000000 (best of 9)

pypy (reverse)
! wall 1.467049 comb 1.460000 user 1.460000 sys 0.000000 (best of 7)
! wall 1.160200 comb 1.170000 user 1.160000 sys 0.010000 (best of 9)

The data clearly shows that it takes less wall and CPU time to resolve
revisions when there are no delta chains in the changelogs, regardless
of the direction of traversal. Furthermore, not using a delta chain
means that fulltext resolution in reverse is as fast as iterating
forward. So not using delta chains on the changelog is a clear CPU win
for reading operations.

An example of a user-visible operation showing this speed-up is revset
evaluation. Here are results for
`hg perfrevset 'author(gps) or author(mpm)'`:

hg
! wall 1.655506 comb 1.660000 user 1.650000 sys 0.010000 (best of 6)
! wall 1.612723 comb 1.610000 user 1.600000 sys 0.010000 (best of 7)

mozilla-central
! wall 17.629826 comb 17.640000 user 17.600000 sys 0.040000 (best of 3)
! wall 17.311033 comb 17.300000 user 17.260000 sys 0.040000 (best of 3)

What about 00changelog.i size?

Repo                Delta Chains     No Delta Chains
hg                    7,033,250         6,976,771
mozilla-central      82,978,748        81,574,623
mozilla-unified      88,112,349        86,702,162
pypy                 20,740,699        20,659,741

The data shows that removing delta chains from the changelog makes the
changelog smaller.

Delta chains are also used during changegroup generation. This
operation essentially converts a series of revisions to one large
delta chain. And changegroup generation is smart: if the delta in
the revlog matches what the changegroup is emitting, it will reuse
the delta instead of recalculating it. We can measure the impact
removing changelog delta chains has on changegroup generation via
`hg perfchangegroupchangelog`:

hg
! wall 1.589245 comb 1.590000 user 1.590000 sys 0.000000 (best of 7)
! wall 1.788060 comb 1.790000 user 1.790000 sys 0.000000 (best of 6)

mozilla-central
! wall 17.382585 comb 17.380000 user 17.340000 sys 0.040000 (best of 3)
! wall 20.161357 comb 20.160000 user 20.120000 sys 0.040000 (best of 3)

mozilla-unified
! wall 18.722839 comb 18.720000 user 18.680000 sys 0.040000 (best of 3)
! wall 21.168075 comb 21.170000 user 21.130000 sys 0.040000 (best of 3)

pypy
! wall 4.828317 comb 4.830000 user 4.820000 sys 0.010000 (best of 3)
! wall 5.415455 comb 5.420000 user 5.410000 sys 0.010000 (best of 3)

The data shows eliminating delta chains makes the changelog part of
changegroup generation slower. This is expected since we now have to
compute deltas for revisions where we could recycle the delta before.

It is worth putting this regression into context of overall changegroup
times. Here is the rough total CPU time spent in changegroup generation
for various repos while using delta chains on the changelog:

Repo              CPU Time (s)    CPU Time w/ compression
hg                  4.50              7.05
mozilla-central   111.1             222.0
pypy               28.68             75.5

Before compression, removing delta chains from the changegroup adds
~4.4% overhead to hg changegroup generation, 1.3% to mozilla-central,
and 2.0% to pypy. When you factor in zlib compression, these percentages
are roughly divided by 2.

While the increased CPU usage for changegroup generation is unfortunate,
I think it is acceptable because the percentage is small, server
operators (those likely impacted most by this) have other mechanisms
to mitigate CPU consumption (namely reducing zlib compression level and
pre-generated clone bundles), and because there is room to optimize this
in the future. For example, we could use the nullid as the base revision,
effectively encoding the full revision for each entry in the changegroup.
When doing this, `hg perfchangegroupchangelog` nearly halves:

mozilla-unified
! wall 21.168075 comb 21.170000 user 21.130000 sys 0.040000 (best of 3)
! wall 11.196461 comb 11.200000 user 11.190000 sys 0.010000 (best of 3)

This looks very promising as a future optimization opportunity.

It's worth that the changes in test-acl.t to the changegroup part size.
This is because revision 6 in the changegroup had a delta chain of
length 2 before and after this patch the base revision is nullrev.
When the base revision is nullrev, cg2packer.deltaparent() hardcodes
the *previous* revision from the changegroup as the delta parent.
This caused the delta in the changegroup to switch base revisions,
the delta to change, and the size to change accordingly. While the
size increased in this case, I think sizes will remain the same
on average, as the delta base for changelog revisions doesn't matter
too much (as this patch shows). So, I don't consider this a regression.

  $ cat <<EOF >> $HGRCPATH
  > [extensions]
  > notify=
  > 
  > [hooks]
  > incoming.notify = python:hgext.notify.hook
  > 
  > [notify]
  > sources = pull
  > diffstat = False
  > 
  > [usersubs]
  > foo@bar = *
  > 
  > [reposubs]
  > * = baz
  > EOF
  $ hg help notify
  notify extension - hooks for sending email push notifications
  
  This extension implements hooks to send email notifications when changesets
  are sent from or received by the local repository.
  
  First, enable the extension as explained in 'hg help extensions', and register
  the hook you want to run. "incoming" and "changegroup" hooks are run when
  changesets are received, while "outgoing" hooks are for changesets sent to
  another repository:
  
    [hooks]
    # one email for each incoming changeset
    incoming.notify = python:hgext.notify.hook
    # one email for all incoming changesets
    changegroup.notify = python:hgext.notify.hook
  
    # one email for all outgoing changesets
    outgoing.notify = python:hgext.notify.hook
  
  This registers the hooks. To enable notification, subscribers must be assigned
  to repositories. The "[usersubs]" section maps multiple repositories to a
  given recipient. The "[reposubs]" section maps multiple recipients to a single
  repository:
  
    [usersubs]
    # key is subscriber email, value is a comma-separated list of repo patterns
    user@host = pattern
  
    [reposubs]
    # key is repo pattern, value is a comma-separated list of subscriber emails
    pattern = user@host
  
  A "pattern" is a "glob" matching the absolute path to a repository, optionally
  combined with a revset expression. A revset expression, if present, is
  separated from the glob by a hash. Example:
  
    [reposubs]
    */widgets#branch(release) = [e-mail]
  
  This sends to "[e-mail]" whenever a changeset on the "release"
  branch triggers a notification in any repository ending in "widgets".
  
  In order to place them under direct user management, "[usersubs]" and
  "[reposubs]" sections may be placed in a separate "hgrc" file and incorporated
  by reference:
  
    [notify]
    config = /path/to/subscriptionsfile
  
  Notifications will not be sent until the "notify.test" value is set to
  "False"; see below.
  
  Notifications content can be tweaked with the following configuration entries:
  
  notify.test
    If "True", print messages to stdout instead of sending them. Default: True.
  
  notify.sources
    Space-separated list of change sources. Notifications are activated only
    when a changeset's source is in this list. Sources may be:
  
    "serve"       changesets received via http or ssh
    "pull"        changesets received via "hg pull"
    "unbundle"    changesets received via "hg unbundle"
    "push"        changesets sent or received via "hg push"
    "bundle"      changesets sent via "hg unbundle"
  
    Default: serve.
  
  notify.strip
    Number of leading slashes to strip from url paths. By default, notifications
    reference repositories with their absolute path. "notify.strip" lets you
    turn them into relative paths. For example, "notify.strip=3" will change
    "/long/path/repository" into "repository". Default: 0.
  
  notify.domain
    Default email domain for sender or recipients with no explicit domain.
  
  notify.style
    Style file to use when formatting emails.
  
  notify.template
    Template to use when formatting emails.
  
  notify.incoming
    Template to use when run as an incoming hook, overriding "notify.template".
  
  notify.outgoing
    Template to use when run as an outgoing hook, overriding "notify.template".
  
  notify.changegroup
    Template to use when running as a changegroup hook, overriding
    "notify.template".
  
  notify.maxdiff
    Maximum number of diff lines to include in notification email. Set to 0 to
    disable the diff, or -1 to include all of it. Default: 300.
  
  notify.maxsubject
    Maximum number of characters in email's subject line. Default: 67.
  
  notify.diffstat
    Set to True to include a diffstat before diff content. Default: True.
  
  notify.merge
    If True, send notifications for merge changesets. Default: True.
  
  notify.mbox
    If set, append mails to this mbox file instead of sending. Default: None.
  
  notify.fromauthor
    If set, use the committer of the first changeset in a changegroup for the
    "From" field of the notification mail. If not set, take the user from the
    pushing repo.  Default: False.
  
  If set, the following entries will also be used to customize the
  notifications:
  
  email.from
    Email "From" address to use if none can be found in the generated email
    content.
  
  web.baseurl
    Root repository URL to combine with repository paths when making references.
    See also "notify.strip".
  
  no commands defined
  $ hg init a
  $ echo a > a/a

commit

  $ hg --cwd a commit -Ama -d '0 0'
  adding a


clone

  $ hg --traceback clone a b
  updating to branch default
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
  $ echo a >> a/a

commit

  $ hg --traceback --cwd a commit -Amb -d '1 0'

on Mac OS X 10.5 the tmp path is very long so would get stripped in the subject line

  $ cat <<EOF >> $HGRCPATH
  > [notify]
  > maxsubject = 200
  > EOF

the python call below wraps continuation lines, which appear on Mac OS X 10.5 because
of the very long subject line
pull (minimal config)

  $ hg --traceback --cwd b pull ../a | \
  >   $PYTHON -c 'import sys,re; print re.sub("\n[\t ]", " ", sys.stdin.read()),'
  pulling from ../a
  searching for changes
  adding changesets
  adding manifests
  adding file changes
  added 1 changesets with 1 changes to 1 files
  Content-Type: text/plain; charset="us-ascii"
  MIME-Version: 1.0
  Content-Transfer-Encoding: 7bit
  Date: * (glob)
  Subject: changeset in $TESTTMP/b: b
  From: test
  X-Hg-Notification: changeset 0647d048b600
  Message-Id: <*> (glob)
  To: baz, foo@bar
  
  changeset 0647d048b600 in $TESTTMP/b (glob)
  details: $TESTTMP/b?cmd=changeset;node=0647d048b600
  description: b
  
  diffs (6 lines):
  
  diff -r cb9a9f314b8b -r 0647d048b600 a
  --- a/a	Thu Jan 01 00:00:00 1970 +0000
  +++ b/a	Thu Jan 01 00:00:01 1970 +0000
  @@ -1,1 +1,2 @@ a
  +a
  (run 'hg update' to get a working copy)
  $ cat <<EOF >> $HGRCPATH
  > [notify]
  > config = `pwd`/.notify.conf
  > domain = test.com
  > strip = 42
  > template = Subject: {desc|firstline|strip}\nFrom: {author}\nX-Test: foo\n\nchangeset {node|short} in {webroot}\ndescription:\n\t{desc|tabindent|strip}
  > 
  > [web]
  > baseurl = http://test/
  > EOF

fail for config file is missing

  $ hg --cwd b rollback
  repository tip rolled back to revision 0 (undo pull)
  $ hg --cwd b pull ../a 2>&1 | grep 'error.*\.notify\.conf' > /dev/null && echo pull failed
  pull failed
  $ touch ".notify.conf"

pull

  $ hg --cwd b rollback
  repository tip rolled back to revision 0 (undo pull)
  $ hg --traceback --cwd b pull ../a  | \
  >   $PYTHON -c 'import sys,re; print re.sub("\n\t", " ", sys.stdin.read()),'
  pulling from ../a
  searching for changes
  adding changesets
  adding manifests
  adding file changes
  added 1 changesets with 1 changes to 1 files
  Content-Type: text/plain; charset="us-ascii"
  MIME-Version: 1.0
  Content-Transfer-Encoding: 7bit
  X-Test: foo
  Date: * (glob)
  Subject: b
  From: [e-mail]
  X-Hg-Notification: changeset 0647d048b600
  Message-Id: <*> (glob)
  To: [e-mail], foo@bar
  
  changeset 0647d048b600 in b
  description: b
  diffs (6 lines):
  
  diff -r cb9a9f314b8b -r 0647d048b600 a
  --- a/a	Thu Jan 01 00:00:00 1970 +0000
  +++ b/a	Thu Jan 01 00:00:01 1970 +0000
  @@ -1,1 +1,2 @@
   a
  +a
  (run 'hg update' to get a working copy)

  $ cat << EOF >> $HGRCPATH
  > [hooks]
  > incoming.notify = python:hgext.notify.hook
  > 
  > [notify]
  > sources = pull
  > diffstat = True
  > EOF

pull

  $ hg --cwd b rollback
  repository tip rolled back to revision 0 (undo pull)
  $ hg --traceback --cwd b pull ../a | \
  >   $PYTHON -c 'import sys,re; print re.sub("\n\t", " ", sys.stdin.read()),'
  pulling from ../a
  searching for changes
  adding changesets
  adding manifests
  adding file changes
  added 1 changesets with 1 changes to 1 files
  Content-Type: text/plain; charset="us-ascii"
  MIME-Version: 1.0
  Content-Transfer-Encoding: 7bit
  X-Test: foo
  Date: * (glob)
  Subject: b
  From: [e-mail]
  X-Hg-Notification: changeset 0647d048b600
  Message-Id: <*> (glob)
  To: [e-mail], foo@bar
  
  changeset 0647d048b600 in b
  description: b
  diffstat:
  
   a |  1 +
   1 files changed, 1 insertions(+), 0 deletions(-)
  
  diffs (6 lines):
  
  diff -r cb9a9f314b8b -r 0647d048b600 a
  --- a/a	Thu Jan 01 00:00:00 1970 +0000
  +++ b/a	Thu Jan 01 00:00:01 1970 +0000
  @@ -1,1 +1,2 @@
   a
  +a
  (run 'hg update' to get a working copy)

test merge

  $ cd a
  $ hg up -C 0
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
  $ echo a >> a
  $ hg ci -Am adda2 -d '2 0'
  created new head
  $ hg merge
  0 files updated, 0 files merged, 0 files removed, 0 files unresolved
  (branch merge, don't forget to commit)
  $ hg ci -m merge -d '3 0'
  $ cd ..
  $ hg --traceback --cwd b pull ../a | \
  >   $PYTHON -c 'import sys,re; print re.sub("\n\t", " ", sys.stdin.read()),'
  pulling from ../a
  searching for changes
  adding changesets
  adding manifests
  adding file changes
  added 2 changesets with 0 changes to 0 files
  Content-Type: text/plain; charset="us-ascii"
  MIME-Version: 1.0
  Content-Transfer-Encoding: 7bit
  X-Test: foo
  Date: * (glob)
  Subject: adda2
  From: [e-mail]
  X-Hg-Notification: changeset 0a184ce6067f
  Message-Id: <*> (glob)
  To: [e-mail], foo@bar
  
  changeset 0a184ce6067f in b
  description: adda2
  diffstat:
  
   a |  1 +
   1 files changed, 1 insertions(+), 0 deletions(-)
  
  diffs (6 lines):
  
  diff -r cb9a9f314b8b -r 0a184ce6067f a
  --- a/a	Thu Jan 01 00:00:00 1970 +0000
  +++ b/a	Thu Jan 01 00:00:02 1970 +0000
  @@ -1,1 +1,2 @@
   a
  +a
  Content-Type: text/plain; charset="us-ascii"
  MIME-Version: 1.0
  Content-Transfer-Encoding: 7bit
  X-Test: foo
  Date: * (glob)
  Subject: merge
  From: [e-mail]
  X-Hg-Notification: changeset 6a0cf76b2701
  Message-Id: <*> (glob)
  To: [e-mail], foo@bar
  
  changeset 6a0cf76b2701 in b
  description: merge
  (run 'hg update' to get a working copy)

non-ascii content and truncation of multi-byte subject

  $ cat <<EOF >> $HGRCPATH
  > [notify]
  > maxsubject = 4
  > EOF
  $ echo a >> a/a
  $ hg --cwd a --encoding utf-8 commit -A -d '0 0' \
  >   -m `$PYTHON -c 'print "\xc3\xa0\xc3\xa1\xc3\xa2\xc3\xa3\xc3\xa4"'`
  $ hg --traceback --cwd b --encoding utf-8 pull ../a | \
  >   $PYTHON -c 'import sys,re; print re.sub("\n\t", " ", sys.stdin.read()),'
  pulling from ../a
  searching for changes
  adding changesets
  adding manifests
  adding file changes
  added 1 changesets with 1 changes to 1 files
  Content-Type: text/plain; charset="us-ascii"
  MIME-Version: 1.0
  Content-Transfer-Encoding: 8bit
  X-Test: foo
  Date: * (glob)
  Subject: \xc3\xa0... (esc)
  From: [e-mail]
  X-Hg-Notification: changeset 7ea05ad269dc
  Message-Id: <*> (glob)
  To: [e-mail], foo@bar
  
  changeset 7ea05ad269dc in b
  description: \xc3\xa0\xc3\xa1\xc3\xa2\xc3\xa3\xc3\xa4 (esc)
  diffstat:
  
   a |  1 +
   1 files changed, 1 insertions(+), 0 deletions(-)
  
  diffs (7 lines):
  
  diff -r 6a0cf76b2701 -r 7ea05ad269dc a
  --- a/a	Thu Jan 01 00:00:03 1970 +0000
  +++ b/a	Thu Jan 01 00:00:00 1970 +0000
  @@ -1,2 +1,3 @@
   a
   a
  +a
  (run 'hg update' to get a working copy)

long lines

  $ cat <<EOF >> $HGRCPATH
  > [notify]
  > maxsubject = 67
  > test = False
  > mbox = mbox
  > EOF
  $ $PYTHON -c 'file("a/a", "ab").write("no" * 500 + "\n")'
  $ hg --cwd a commit -A -m "long line"
  $ hg --traceback --cwd b pull ../a
  pulling from ../a
  searching for changes
  adding changesets
  adding manifests
  adding file changes
  added 1 changesets with 1 changes to 1 files
  notify: sending 2 subscribers 1 changes
  (run 'hg update' to get a working copy)
  $ $PYTHON -c 'import sys,re; print re.sub("\n\t", " ", file("b/mbox").read()),'
  From [e-mail] ... ... .. ..:..:.. .... (re)
  Content-Type: text/plain; charset="us-ascii"
  MIME-Version: 1.0
  Content-Transfer-Encoding: quoted-printable
  X-Test: foo
  Date: * (glob)
  Subject: long line
  From: [e-mail]
  X-Hg-Notification: changeset e0be44cf638b
  Message-Id: <hg.e0be44cf638b.*.*@*> (glob)
  To: [e-mail], foo@bar
  
  changeset e0be44cf638b in b
  description: long line
  diffstat:
  
   a |  1 +
   1 files changed, 1 insertions(+), 0 deletions(-)
  
  diffs (8 lines):
  
  diff -r 7ea05ad269dc -r e0be44cf638b a
  --- a/a	Thu Jan 01 00:00:00 1970 +0000
  +++ b/a	Thu Jan 01 00:00:00 1970 +0000
  @@ -1,3 +1,4 @@
   a
   a
   a
  +nonononononononononononononononononononononononononononononononononononono=
  nononononononononononononononononononononononononononononononononononononon=
  ononononononononononononononononononononononononononononononononononononono=
  nononononononononononononononononononononononononononononononononononononon=
  ononononononononononononononononononononononononononononononononononononono=
  nononononononononononononononononononononononononononononononononononononon=
  ononononononononononononononononononononononononononononononononononononono=
  nononononononononononononononononononononononononononononononononononononon=
  ononononononononononononononononononononononononononononononononononononono=
  nononononononononononononononononononononononononononononononononononononon=
  ononononononononononononononononononononononononononononononononononononono=
  nononononononononononononononononononononononononononononononononononononon=
  ononononononononononononononononononononononononononononononononononononono=
  nonononononononononononono
  
 revset selection: send to address that matches branch and repo

  $ cat << EOF >> $HGRCPATH
  > [hooks]
  > incoming.notify = python:hgext.notify.hook
  > 
  > [notify]
  > sources = pull
  > test = True
  > diffstat = False
  > maxdiff = 0
  > 
  > [reposubs]
  > */a#branch(test) = [e-mail]
  > */b#branch(test) = [e-mail]
  > EOF
  $ hg --cwd a branch test
  marked working directory as branch test
  (branches are permanent and global, did you want a bookmark?)
  $ echo a >> a/a
  $ hg --cwd a ci -m test -d '1 0'
  $ hg --traceback --cwd b pull ../a | \
  >   $PYTHON -c 'import sys,re; print re.sub("\n\t", " ", sys.stdin.read()),'
  pulling from ../a
  searching for changes
  adding changesets
  adding manifests
  adding file changes
  added 1 changesets with 1 changes to 1 files
  Content-Type: text/plain; charset="us-ascii"
  MIME-Version: 1.0
  Content-Transfer-Encoding: 7bit
  X-Test: foo
  Date: * (glob)
  Subject: test
  From: [e-mail]
  X-Hg-Notification: changeset fbbcbc516f2f
  Message-Id: <hg.fbbcbc516f2f.*.*@*> (glob)
  To: [e-mail], foo@bar, [e-mail]
  
  changeset fbbcbc516f2f in b
  description: test
  (run 'hg update' to get a working copy)

revset selection: don't send to address that waits for mails
from different branch

  $ hg --cwd a update default
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
  $ echo a >> a/a
  $ hg --cwd a ci -m test -d '1 0'
  $ hg --traceback --cwd b pull ../a | \
  >   $PYTHON -c 'import sys,re; print re.sub("\n\t", " ", sys.stdin.read()),'
  pulling from ../a
  searching for changes
  adding changesets
  adding manifests
  adding file changes
  added 1 changesets with 0 changes to 0 files (+1 heads)
  Content-Type: text/plain; charset="us-ascii"
  MIME-Version: 1.0
  Content-Transfer-Encoding: 7bit
  X-Test: foo
  Date: * (glob)
  Subject: test
  From: [e-mail]
  X-Hg-Notification: changeset 38b42fa092de
  Message-Id: <hg.38b42fa092de.*.*@*> (glob)
  To: [e-mail], foo@bar
  
  changeset 38b42fa092de in b
  description: test
  (run 'hg heads' to see heads)

default template:

  $ grep -v '^template =' $HGRCPATH > "$HGRCPATH.new"
  $ mv "$HGRCPATH.new" $HGRCPATH
  $ echo a >> a/a
  $ hg --cwd a commit -m 'default template'
  $ hg --cwd b pull ../a -q | \
  >   $PYTHON -c 'import sys,re; print re.sub("\n\t", " ", sys.stdin.read()),'
  Content-Type: text/plain; charset="us-ascii"
  MIME-Version: 1.0
  Content-Transfer-Encoding: 7bit
  Date: * (glob)
  Subject: changeset in b: default template
  From: [e-mail]
  X-Hg-Notification: changeset 3548c9e294b6
  Message-Id: <hg.3548c9e294b6.*.*@*> (glob)
  To: [e-mail], foo@bar
  
  changeset 3548c9e294b6 in $TESTTMP/b (glob)
  details: http://test/b?cmd=changeset;node=3548c9e294b6
  description: default template

with style:

  $ cat <<EOF > notifystyle.map
  > changeset = "Subject: {desc|firstline|strip}
  >              From: {author}
  >              {""}
  >              changeset {node|short}"
  > EOF
  $ cat <<EOF >> $HGRCPATH
  > [notify]
  > style = $TESTTMP/notifystyle.map
  > EOF
  $ echo a >> a/a
  $ hg --cwd a commit -m 'with style'
  $ hg --cwd b pull ../a -q | \
  >   $PYTHON -c 'import sys,re; print re.sub("\n\t", " ", sys.stdin.read()),'
  Content-Type: text/plain; charset="us-ascii"
  MIME-Version: 1.0
  Content-Transfer-Encoding: 7bit
  Date: * (glob)
  Subject: with style
  From: [e-mail]
  X-Hg-Notification: changeset e917dbd961d3
  Message-Id: <hg.e917dbd961d3.*.*@*> (glob)
  To: [e-mail], foo@bar
  
  changeset e917dbd961d3

with template (overrides style):

  $ cat <<EOF >> $HGRCPATH
  > template = Subject: {node|short}: {desc|firstline|strip}
  >            From: {author}
  >            {""}
  >            {desc}
  > EOF
  $ echo a >> a/a
  $ hg --cwd a commit -m 'with template'
  $ hg --cwd b pull ../a -q | \
  >   $PYTHON -c 'import sys,re; print re.sub("\n\t", " ", sys.stdin.read()),'
  Content-Type: text/plain; charset="us-ascii"
  MIME-Version: 1.0
  Content-Transfer-Encoding: 7bit
  Date: * (glob)
  Subject: a09743fd3edd: with template
  From: [e-mail]
  X-Hg-Notification: changeset a09743fd3edd
  Message-Id: <hg.a09743fd3edd.*.*@*> (glob)
  To: [e-mail], foo@bar
  
  with template