view tests/test-amend-subrepo.t @ 46607:e9901d01d135

revlog: add a mechanism to verify expected file position before appending

If someone uses `hg debuglocks`, or some non-hg process writes to the .hg
directory without respecting the locks, or if the repo's on a networked
filesystem, it's possible for the revlog code to write out corrupted data.

The form of this corruption can vary depending on what data was written and how
that happened. We are in the "networked filesystem" case (though I've had users
also do this to themselves with the "`hg debuglocks`" scenario), and most often
see this with the changelog. What ends up happening is we produce two items
(let's call them rev1 and rev2) in the .i file that have the same linkrev,
baserev, and offset into the .d file, while the data in the .d file is appended
properly. rev2's compressed_size is accurate for rev2, but when we go to
decompress the data in the .d file, we use the offset that's recorded in the
index file, which is the same as rev1, and attempt to decompress
rev2.compressed_size bytes of rev1's data. This usually does not succeed. :)

When using inline data, this also fails, though I haven't investigated why too
closely. This shows up as a "patch decode" error. I believe what's happening
there is that we're basically ignoring the offset field, getting the data
properly, but since baserev != rev, it thinks this is a delta based on rev
(instead of a full text) and can't actually apply it as such.

For now, I'm going to make this an optional component and default it to entirely
off. I may increase the default severity of this in the future, once I've
enabled it for my users and we gain more experience with it. Luckily, most of my
users have a versioned filesystem and can roll back to before the corruption has
been written, it's just a hassle to do so and not everyone knows how (so it's a
support burden). Users on other filesystems will not have that luxury, and this
can cause them to have a corrupted repository that they are unlikely to know how
to resolve, and they'll see this as a data-loss event. Refusing to create the
corruption is a much better user experience.

This mechanism is not perfect. There may be false-negatives (racy writes that
are not detected). There should not be any false-positives (non-racy writes that
are detected as such). This is not a mechanism that makes putting a repo on a
networked filesystem "safe" or "supported", just *less* likely to cause
corruption.

Differential Revision: https://phab.mercurial-scm.org/D9952

#testcases obsstore-off obsstore-on

  $ cat << EOF >> $HGRCPATH
  > [extensions]
  > amend =
  > EOF

#if obsstore-on
  $ cat << EOF >> $HGRCPATH
  > [experimental]
  > evolution.createmarkers = True
  > EOF
#endif

Prepare parent repo
-------------------

  $ hg init r
  $ cd r

  $ echo a > a
  $ hg ci -Am0
  adding a

Link first subrepo
------------------

  $ echo 's = s' >> .hgsub
  $ hg add .hgsub
  $ hg init s

amend without .hgsub

  $ hg amend s
  abort: can't commit subrepos without .hgsub
  [255]

amend with subrepo

  $ hg amend
  saved backup bundle to * (glob) (obsstore-off !)
  $ hg status --change .
  A .hgsub
  A .hgsubstate
  A a
  $ cat .hgsubstate
  0000000000000000000000000000000000000000 s

Update subrepo
--------------

add new commit to be amended

  $ echo a >> a
  $ hg ci -m1

amend with dirty subrepo

  $ echo a >> s/a
  $ hg add -R s
  adding s/a
  $ hg amend
  abort: uncommitted changes in subrepository "s"
  (use --subrepos for recursive commit)
  [255]

amend with modified subrepo

  $ hg ci -R s -m0
  $ hg amend
  saved backup bundle to * (glob) (obsstore-off !)
  $ hg status --change .
  M .hgsubstate
  M a
  $ cat .hgsubstate
  f7b1eb17ad24730a1651fccd46c43826d1bbc2ac s

revert subrepo change

  $ hg up -R s -q null
  $ hg amend
  saved backup bundle to * (glob) (obsstore-off !)
  $ hg status --change .
  M a

Link another subrepo
--------------------

add new commit to be amended

  $ echo b >> b
  $ hg ci -qAm2

also checks if non-subrepo change is included

  $ echo a >> a

amend with another subrepo

  $ hg init t
  $ echo b >> t/b
  $ hg ci -R t -Am0
  adding b
  $ echo 't = t' >> .hgsub
  $ hg amend
  saved backup bundle to * (glob) (obsstore-off !)
  $ hg status --change .
  M .hgsub
  M .hgsubstate
  M a
  A b
  $ cat .hgsubstate
  0000000000000000000000000000000000000000 s
  bfb1a4fb358498a9533dabf4f2043d94162f1fcd t

Unlink one subrepo
------------------

add new commit to be amended

  $ echo a >> a
  $ hg ci -m3

  $ echo 't = t' > .hgsub

--interactive won't silently ignore dirty subrepos

  $ echo modified > t/b
  $ hg amend --interactive --config ui.interactive=True
  abort: uncommitted changes in subrepository "t"
  [255]
  $ hg amend --interactive --config ui.interactive=True --config ui.commitsubrepos=True
  abort: uncommitted changes in subrepository "t"
  [255]

  $ hg -R t revert -q --all --no-backup

amend with one subrepo dropped

  $ hg amend
  saved backup bundle to * (glob) (obsstore-off !)
  $ hg status --change .
  M .hgsub
  M .hgsubstate
  M a
  $ cat .hgsubstate
  bfb1a4fb358498a9533dabf4f2043d94162f1fcd t

Unlink subrepos completely
--------------------------

add new commit to be amended

  $ echo a >> a
  $ hg ci -m3

amend with .hgsub removed

  $ hg rm .hgsub
  $ hg amend
  saved backup bundle to * (glob) (obsstore-off !)
  $ hg status --change .
  M a
  R .hgsub
  R .hgsubstate

broken repositories will refuse to push

#if obsstore-off
  $ hg up -q -C 2
#else
  $ hg up -q -C 6
#endif
  $ echo c >> t/b
  $ hg amend -q -R t

  $ hg init ../dest
  $ hg init ../dest/t
  $ hg init ../dest/s
  $ hg push -q ../dest
  abort: subrepo 't' is hidden in revision 04aa62396ec6 (obsstore-on !)
  abort: subrepo 't' not found in revision 04aa62396ec6 (obsstore-off !)
  [255]

... unless forced

  $ hg push --force -q ../dest
  $ hg verify -R ../dest
  checking changesets
  checking manifests
  crosschecking files in changesets and manifests
  checking files
  checked 5 changesets with 12 changes to 4 files
  checking subrepo links
  subrepo 't' not found in revision 04aa62396ec6
  subrepo 't' not found in revision 6bce99600681

  $ cd ..