view tests/test-symlinks.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

#require symlink

== tests added in 0.7 ==

  $ hg init test-symlinks-0.7; cd test-symlinks-0.7;
  $ touch foo; ln -s foo bar; ln -s nonexistent baz

import with add and addremove -- symlink walking should _not_ screwup.

  $ hg add
  adding bar
  adding baz
  adding foo
  $ hg forget bar baz foo
  $ hg addremove
  adding bar
  adding baz
  adding foo

commit -- the symlink should _not_ appear added to dir state

  $ hg commit -m 'initial'

  $ touch bomb

again, symlink should _not_ show up on dir state

  $ hg addremove
  adding bomb

Assert screamed here before, should go by without consequence

  $ hg commit -m 'is there a bug?'
  $ cd ..


== fifo & ignore ==

  $ hg init test; cd test;

  $ mkdir dir
  $ touch a.c dir/a.o dir/b.o

test what happens if we want to trick hg

  $ hg commit -A -m 0
  adding a.c
  adding dir/a.o
  adding dir/b.o
  $ echo "relglob:*.o" > .hgignore
  $ rm a.c
  $ rm dir/a.o
  $ rm dir/b.o
  $ mkdir dir/a.o
  $ ln -s nonexistent dir/b.o
  $ mkfifo a.c

it should show a.c, dir/a.o and dir/b.o deleted

  $ hg status
  M dir/b.o
  ! a.c
  ! dir/a.o
  ? .hgignore
  $ hg status a.c
  a.c: unsupported file type (type is fifo)
  ! a.c
  $ cd ..


== symlinks from outside the tree ==

test absolute path through symlink outside repo

  $ p=`pwd`
  $ hg init x
  $ ln -s x y
  $ cd x
  $ touch f
  $ hg add f
  $ hg status "$p"/y/f
  A f

try symlink outside repo to file inside

  $ ln -s x/f ../z

this should fail

  $ hg status ../z && { echo hg mistakenly exited with status 0; exit 1; } || :
  abort: ../z not under root '$TESTTMP/x'
  $ cd ..


== cloning symlinks ==
  $ hg init clone; cd clone;

try cloning symlink in a subdir
1. commit a symlink

  $ mkdir -p a/b/c
  $ cd a/b/c
  $ ln -s /path/to/symlink/source demo
  $ cd ../../..
  $ hg stat
  ? a/b/c/demo
  $ hg commit -A -m 'add symlink in a/b/c subdir'
  adding a/b/c/demo

2. clone it

  $ cd ..
  $ hg clone clone clonedest
  updating to branch default
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved


== symlink and git diffs ==

git symlink diff

  $ cd clonedest
  $ hg diff --git -r null:tip
  diff --git a/a/b/c/demo b/a/b/c/demo
  new file mode 120000
  --- /dev/null
  +++ b/a/b/c/demo
  @@ -0,0 +1,1 @@
  +/path/to/symlink/source
  \ No newline at end of file
  $ hg export --git tip > ../sl.diff

import git symlink diff

  $ hg rm a/b/c/demo
  $ hg commit -m'remove link'
  $ hg import ../sl.diff
  applying ../sl.diff
  $ hg diff --git -r 1:tip
  diff --git a/a/b/c/demo b/a/b/c/demo
  new file mode 120000
  --- /dev/null
  +++ b/a/b/c/demo
  @@ -0,0 +1,1 @@
  +/path/to/symlink/source
  \ No newline at end of file

== symlinks and addremove ==

directory moved and symlinked

  $ mkdir foo
  $ touch foo/a
  $ hg ci -Ama
  adding foo/a
  $ mv foo bar
  $ ln -s bar foo
  $ hg status
  ! foo/a
  ? bar/a
  ? foo

now addremove should remove old files

  $ hg addremove
  adding bar/a
  adding foo
  removing foo/a

commit and update back

  $ hg ci -mb
  $ hg up '.^'
  1 files updated, 0 files merged, 2 files removed, 0 files unresolved
  $ hg up tip
  2 files updated, 0 files merged, 1 files removed, 0 files unresolved

  $ cd ..

== root of repository is symlinked ==

  $ hg init root
  $ ln -s root link
  $ cd root
  $ echo foo > foo
  $ hg status
  ? foo
  $ hg status ../link
  ? foo
  $ hg add foo
  $ hg cp foo "$TESTTMP/link/bar"
  foo has not been committed yet, so no copy data will be stored for bar.
  $ cd ..


  $ hg init b
  $ cd b
  $ ln -s nothing dangling
  $ hg commit -m 'commit symlink without adding' dangling
  abort: dangling: file not tracked!
  [10]
  $ hg add dangling
  $ hg commit -m 'add symlink'

  $ hg tip -v
  changeset:   0:cabd88b706fc
  tag:         tip
  user:        test
  date:        Thu Jan 01 00:00:00 1970 +0000
  files:       dangling
  description:
  add symlink
  
  
  $ hg manifest --debug
  2564acbe54bbbedfbf608479340b359f04597f80 644 @ dangling
  $ readlink.py dangling
  dangling -> nothing

  $ rm dangling
  $ ln -s void dangling
  $ hg commit -m 'change symlink'
  $ readlink.py dangling
  dangling -> void


modifying link

  $ rm dangling
  $ ln -s empty dangling
  $ readlink.py dangling
  dangling -> empty


reverting to rev 0:

  $ hg revert -r 0 -a
  reverting dangling
  $ readlink.py dangling
  dangling -> nothing


backups:

  $ readlink.py *.orig
  dangling.orig -> empty
  $ rm *.orig
  $ hg up -C
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved

copies

  $ hg cp -v dangling dangling2
  copying dangling to dangling2
  $ hg st -Cmard
  A dangling2
    dangling
  $ readlink.py dangling dangling2
  dangling -> void
  dangling2 -> void


Issue995: hg copy -A incorrectly handles symbolic links

  $ hg up -C
  0 files updated, 0 files merged, 0 files removed, 0 files unresolved
  $ mkdir dir
  $ ln -s dir dirlink
  $ hg ci -qAm 'add dirlink'
  $ mkdir newdir
  $ mv dir newdir/dir
  $ mv dirlink newdir/dirlink
  $ hg mv -A dirlink newdir/dirlink

  $ cd ..