tests/test-clone-pull-corruption.t

doc: add the tool to check section marks in help documents

This patch adds "doc/check-seclevel.py" which checks below in help
documents:

  - whether unknown or unavailable section marks are used or not
  - whether appropriate section mark is used at sub-sectioning

It should be invoked in "doc" directory.

It checks all help documents of Mercurial (topics, commands,
extensions), if no file is specified by --file option.

With --file option, it checks contents of the specified file as help
document, for self testing purpose: -t/-c/-e/-C are used to specify
what kind of help document contents of the specified file is.

This checking is related to changeset 979b107eaea2.

Corrupt an hg repo with a pull started during an aborted commit
Create two repos, so that one of them can pull from the other one.

  $ hg init source
  $ cd source
  $ touch foo
  $ hg add foo
  $ hg ci -m 'add foo'
  $ hg clone . ../corrupted
  updating to branch default
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
  $ echo >> foo
  $ hg ci -m 'change foo'

Add a hook to wait 5 seconds and then abort the commit

  $ cd ../corrupted
  $ echo "[hooks]" >> .hg/hgrc
  $ echo "pretxncommit = sh -c 'sleep 5; exit 1'" >> .hg/hgrc

start a commit...

  $ touch bar
  $ hg add bar
  $ hg ci -m 'add bar' &

... and start a pull while the commit is still running

  $ sleep 1
  $ hg pull ../source 2>/dev/null
  pulling from ../source
  transaction abort!
  rollback completed
  abort: pretxncommit hook exited with status 1
  searching for changes
  adding changesets
  adding manifests
  adding file changes
  added 1 changesets with 1 changes to 1 files
  (run 'hg update' to get a working copy)

see what happened

  $ wait
  $ hg verify
  checking changesets
  checking manifests
  crosschecking files in changesets and manifests
  checking files
  1 files, 2 changesets, 2 total revisions

  $ cd ..