view tests/test-import-eol.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

  $ cat > makepatch.py <<EOF
  > import sys
  > f = open(sys.argv[2], 'wb')
  > w = f.write
  > w(b'test message\n')
  > w(b'diff --git a/a b/a\n')
  > w(b'--- a/a\n')
  > w(b'+++ b/a\n')
  > w(b'@@ -1,5 +1,5 @@\n')
  > w(b' a\n')
  > w(b'-bbb\r\n')
  > w(b'+yyyy\r\n')
  > w(b' cc\r\n')
  > w({'empty:lf': b' \n',
  >    'empty:crlf': b' \r\n',
  >    'empty:stripped-lf': b'\n',
  >    'empty:stripped-crlf': b'\r\n'}[sys.argv[1]])
  > w(b' d\n')
  > w(b'-e\n')
  > w(b'\\\\ No newline at end of file\n')
  > w(b'+z\r\n')
  > w(b'\\\\ No newline at end of file\r\n')
  > EOF

  $ hg init repo
  $ cd repo
  $ echo '\.diff' > .hgignore


Test different --eol values

  $ "$PYTHON" -c 'open("a", "wb").write(b"a\nbbb\ncc\n\nd\ne")'
  $ hg ci -Am adda
  adding .hgignore
  adding a
  $ "$PYTHON" ../makepatch.py empty:lf eol.diff
  $ "$PYTHON" ../makepatch.py empty:crlf eol-empty-crlf.diff
  $ "$PYTHON" ../makepatch.py empty:stripped-lf eol-empty-stripped-lf.diff
  $ "$PYTHON" ../makepatch.py empty:stripped-crlf eol-empty-stripped-crlf.diff

invalid eol

  $ hg --config patch.eol='LFCR' import eol.diff
  applying eol.diff
  abort: unsupported line endings type: LFCR
  [255]
  $ hg revert -a


force LF

  $ hg --traceback --config patch.eol='LF' import eol.diff
  applying eol.diff
  $ hg id
  9e4ef7b3d4af tip
  $ cat a
  a
  yyyy
  cc
  
  d
  e (no-eol)
  $ hg st

 (test empty-line variants: all of them should generate the same revision)

  $ hg up -qC 0
  $ hg --config patch.eol='LF' import eol-empty-crlf.diff
  applying eol-empty-crlf.diff
  $ hg id
  9e4ef7b3d4af tip

  $ hg up -qC 0
  $ hg --config patch.eol='LF' import eol-empty-stripped-lf.diff
  applying eol-empty-stripped-lf.diff
  $ hg id
  9e4ef7b3d4af tip

  $ hg up -qC 0
  $ hg --config patch.eol='LF' import eol-empty-stripped-crlf.diff
  applying eol-empty-stripped-crlf.diff
  $ hg id
  9e4ef7b3d4af tip

force CRLF

  $ hg up -C 0
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
  $ hg --traceback --config patch.eol='CRLF' import eol.diff
  applying eol.diff
  $ cat a
  a\r (esc)
  yyyy\r (esc)
  cc\r (esc)
  \r (esc)
  d\r (esc)
  e (no-eol)
  $ hg st


auto EOL on LF file

  $ hg up -C 0
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
  $ hg --traceback --config patch.eol='auto' import eol.diff
  applying eol.diff
  $ cat a
  a
  yyyy
  cc
  
  d
  e (no-eol)
  $ hg st


auto EOL on CRLF file

  $ "$PYTHON" -c 'open("a", "wb").write(b"a\r\nbbb\r\ncc\r\n\r\nd\r\ne")'
  $ hg commit -m 'switch EOLs in a'
  $ hg --traceback --config patch.eol='auto' import eol.diff
  applying eol.diff
  $ cat a
  a\r (esc)
  yyyy\r (esc)
  cc\r (esc)
  \r (esc)
  d\r (esc)
  e (no-eol)
  $ hg st


auto EOL on new file or source without any EOL

  $ "$PYTHON" -c 'open("noeol", "wb").write(b"noeol")'
  $ hg add noeol
  $ hg commit -m 'add noeol'
  $ "$PYTHON" -c 'open("noeol", "wb").write(b"noeol\r\nnoeol\n")'
  $ "$PYTHON" -c 'open("neweol", "wb").write(b"neweol\nneweol\r\n")'
  $ hg add neweol
  $ hg diff --git > noeol.diff
  $ hg revert --no-backup noeol neweol
  $ rm neweol
  $ hg --traceback --config patch.eol='auto' import -m noeol noeol.diff
  applying noeol.diff
  $ cat noeol
  noeol\r (esc)
  noeol
  $ cat neweol
  neweol
  neweol\r (esc)
  $ hg st


Test --eol and binary patches

  $ "$PYTHON" -c 'open("b", "wb").write(b"a\x00\nb\r\nd")'
  $ hg ci -Am addb
  adding b
  $ "$PYTHON" -c 'open("b", "wb").write(b"a\x00\nc\r\nd")'
  $ hg diff --git > bin.diff
  $ hg revert --no-backup b

binary patch with --eol

  $ hg import --config patch.eol='CRLF' -m changeb bin.diff
  applying bin.diff
  $ cat b
  a\x00 (esc)
  c\r (esc)
  d (no-eol)
  $ hg st
  $ cd ..