commands: make commit acquire locks before processing (issue4368) Before this patch, "hg commit" (process A) executes steps below: 1. get current branch heads via 'repo.branchheads()' - cache 'repo.changelog' 2. invoke 'repo.commit()' 3. acquire wlock - invalidate 'repo.dirstate' 4. access 'repo.dirstate' - re-read '.hg/dirstate' - check validity of parent revisions with 'repo.changelog' 5. invoke 'repo.commitctx()' 6. acquire store lock (slock) - invalidate 'repo.changelog' 7. do committing 8. release slock 9. release wlock 10. check new branch head (via 'cmdutil.commitstatus()') If acquisition of wlock at (3) above waits for another "hg commit" (process B) or so running parallelly to release wlock, process A causes creating orphan revision, because: - '.hg/dirstate' refers the revision, which is newly added by process B, as its parent - but already cached 'repo.changelog' doesn't contain such revision - therefore, validating parents of '.hg/dirstate' at (4) above replaces such revision with 'nullid' Then, process A creates "orphan" revision, of which parent is "null" revision. In addition to it, "created new head" may be shown at the end of process A unintentionally, if store is updated parallelly, because both getting branch heads (1) and checking new branch head (10) are executed outside slock scope. To avoid this issue, this patch makes "hg commit" acquire wlock and slock before processing. This patch resolves the issue between "hg commit" processes, but not one between "hg commit" and other commands. Subsequent patches resolve the latter. Even after this patch, there are still corner case problems below: - filecache may overlook changes of '.hg/dirstate', and it causes similar issue (see below for detail) https://bz.mercurial-scm.org/show_bug.cgi?id=4368#c10 - 3rd party extension may cause similar issue, if it directly uses 'repo.commit()' without acquisition of wlock and slock This can be fixed by acquisition of slock at the beginning of 'repo.commit()', but it seems suitable for "default" branch In fact, acquisition of slock itself is already introduced at "default" branch by 4414d500604f, but acquisition is not at the beginning of 'repo.commit()'. This patch also changes some tests: - test-fncache.t needs this tricky wrapping, to release (= forced failure of) wlock certainly - order of "hg commit" output is changed by widening scope of locks, because some hooks are fired after releasing wlock

https://bz.mercurial-scm.org/2137

Setup:

create a little extension that has 3 side-effects:
1) ensure changelog data is not inlined
2) make revlog to use lazyparser
3) test that repo.lookup() works
1 and 2 are preconditions for the bug; 3 is the bug.

  $ cat > commitwrapper.py <<EOF
  > from mercurial import extensions, node, revlog
  > 
  > def reposetup(ui, repo):
  >     class wraprepo(repo.__class__):
  >         def commit(self, *args, **kwargs):
  >             result = super(wraprepo, self).commit(*args, **kwargs)
  >             tip1 = node.short(repo.changelog.tip())
  >             tip2 = node.short(repo.lookup(tip1))
  >             assert tip1 == tip2
  >             ui.write('new tip: %s\n' % tip1)
  >             return result
  >     repo.__class__ = wraprepo
  > 
  > def extsetup(ui):
  >     revlog._maxinline = 8             # split out 00changelog.d early
  >     revlog._prereadsize = 8           # use revlog.lazyparser
  > EOF

  $ cat >> $HGRCPATH <<EOF
  > [extensions]
  > commitwrapper = `pwd`/commitwrapper.py
  > EOF

  $ hg init repo1
  $ cd repo1
  $ echo a > a
  $ hg commit -A -m'add a with a long commit message to make the changelog a bit bigger'
  adding a
  new tip: 553596fad57b

Test that new changesets are visible to repo.lookup():

  $ echo a >> a
  $ hg commit -m'one more commit to demonstrate the bug'
  new tip: 799ae3599e0e

  $ hg tip
  changeset:   1:799ae3599e0e
  tag:         tip
  user:        test
  date:        Thu Jan 01 00:00:00 1970 +0000
  summary:     one more commit to demonstrate the bug
  

  $ cd ..