view tests/test-merge-exec.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

===============================================
Testing merge involving change to the exec flag
===============================================

#require execbit


Initial setup
==============


  $ hg init base-repo
  $ cd base-repo
  $ cat << EOF > a
  > 1
  > 2
  > 3
  > 4
  > 5
  > 6
  > 7
  > 8
  > 9
  > EOF
  $ touch b
  $ hg add a b
  $ hg commit -m "initial commit"
  $ cd ..

  $ hg init base-exec
  $ cd base-exec
  $ cat << EOF > a
  > 1
  > 2
  > 3
  > 4
  > 5
  > 6
  > 7
  > 8
  > 9
  > EOF
  $ chmod +x a
  $ touch b
  $ hg add a b
  $ hg commit -m "initial commit"
  $ cd ..

Testing merging mode change
===========================

Adding the flag
---------------

setup

Change on one side, executable bit on the other

  $ hg clone base-repo simple-merge-repo
  updating to branch default
  2 files updated, 0 files merged, 0 files removed, 0 files unresolved
  $ cd simple-merge-repo
  $ chmod +x a
  $ hg ci -m "make a executable, no change"
  $ [ -x a ] || echo "executable bit not recorded"
  $ hg up ".^"
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
  $ cat << EOF > a
  > 1
  > 2
  > 3
  > 4
  > 5
  > 6
  > 7
  > x
  > 9
  > EOF
  $ hg commit -m "edit end of file"
  created new head

merge them (from the update side)

  $ hg merge 'desc("make a executable, no change")'
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
  (branch merge, don't forget to commit)
  $ hg st
  M a
  $ [ -x a ] || echo "executable bit lost"

merge them (from the chmod side)

  $ hg up -C 'desc("make a executable, no change")'
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
  $ hg merge 'desc("edit end of file")'
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
  (branch merge, don't forget to commit)
  $ hg st
  M a
  $ [ -x a ] || echo "executable bit lost"


  $ cd ..


Removing the flag
-----------------

Change on one side, executable bit on the other

  $ hg clone base-exec simple-merge-repo-removal
  updating to branch default
  2 files updated, 0 files merged, 0 files removed, 0 files unresolved
  $ cd simple-merge-repo-removal
  $ chmod -x a
  $ hg ci -m "make a non-executable, no change"
  $ [ -x a ] && echo "executable bit not removed"
  [1]
  $ hg up ".^"
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
  $ cat << EOF > a
  > 1
  > 2
  > 3
  > 4
  > 5
  > 6
  > 7
  > x
  > 9
  > EOF
  $ hg commit -m "edit end of file"
  created new head

merge them (from the update side)

  $ hg merge 'desc("make a non-executable, no change")'
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
  (branch merge, don't forget to commit)
  $ hg st
  M a
  $ [ -x a ] && echo "executable bit not removed"
  [1]

merge them (from the chmod side)

  $ hg up -C 'desc("make a non-executable, no change")'
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
  $ hg merge 'desc("edit end of file")'
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
  (branch merge, don't forget to commit)
  $ hg st
  M a
  $ [ -x a ] && echo "executable bit not removed"
  [1]


  $ cd ..

Testing merging mode change with rename
=======================================

Adding the flag
---------------

  $ hg clone base-repo rename-merge-repo
  updating to branch default
  2 files updated, 0 files merged, 0 files removed, 0 files unresolved
  $ cd rename-merge-repo

make "a" executable on one side

  $ chmod +x a
  $ hg status
  M a
  $ hg ci -m "make a executable"
  $ [ -x a ] || echo "executable bit not recorded"
  $ hg up ".^"
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved

make "a" renamed on the other side

  $ hg mv a z
  $ hg st --copies
  A z
    a
  R a
  $ hg ci -m "rename a to z"
  created new head

merge them (from the rename side)

  $ hg merge 'desc("make a executable")'
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
  (branch merge, don't forget to commit)
  $ hg st --copies
  M z
    a
  $ [ -x z ] || echo "executable bit lost"

merge them (from the chmod side)

  $ hg up -C 'desc("make a executable")'
  1 files updated, 0 files merged, 1 files removed, 0 files unresolved
  $ hg merge 'desc("rename a to z")'
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
  (branch merge, don't forget to commit)
  $ hg st --copies
  M z
    a
  R a
  $ [ -x z ] || echo "executable bit lost"


  $ cd ..

Removing the flag
-----------------

  $ hg clone base-exec rename-merge-repo-removal
  updating to branch default
  2 files updated, 0 files merged, 0 files removed, 0 files unresolved
  $ cd rename-merge-repo-removal

make "a" non-executable on one side

  $ chmod -x a
  $ hg status
  M a
  $ hg ci -m "make a non-executable"
  $ [ -x a ] && echo "executable bit not removed"
  [1]
  $ hg up ".^"
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved

make "a" renamed on the other side

  $ hg mv a z
  $ hg st --copies
  A z
    a
  R a
  $ hg ci -m "rename a to z"
  created new head

merge them (from the rename side)

  $ hg merge 'desc("make a non-executable")'
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
  (branch merge, don't forget to commit)
  $ hg st --copies
  M z
    a
  $ [ -x z ] && echo "executable bit not removed"
  [1]

merge them (from the chmod side)

  $ hg up -C 'desc("make a non-executable")'
  1 files updated, 0 files merged, 1 files removed, 0 files unresolved
  $ hg merge 'desc("rename a to z")'
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
  (branch merge, don't forget to commit)
  $ hg st --copies
  M z
    a
  R a
  $ [ -x z ] && echo "executable bit not removed"
  [1]


  $ cd ..


Testing merging mode change with rename + modification on both side
===================================================================


Adding the flag
---------------

  $ hg clone base-repo rename+mod-merge-repo
  updating to branch default
  2 files updated, 0 files merged, 0 files removed, 0 files unresolved
  $ cd rename+mod-merge-repo

make "a" executable on one side

  $ chmod +x a
  $ cat << EOF > a
  > 1
  > x
  > 3
  > 4
  > 5
  > 6
  > 7
  > 8
  > 9
  > EOF
  $ hg status
  M a
  $ hg ci -m "make a executable, and change start"
  $ [ -x a ] || echo "executable bit not recorded"
  $ hg up ".^"
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved

make "a" renamed on the other side

  $ hg mv a z
  $ hg st --copies
  A z
    a
  R a
  $ cat << EOF > z
  > 1
  > 2
  > 3
  > 4
  > 5
  > 6
  > 7
  > x
  > 9
  > EOF
  $ hg ci -m "rename a to z, and change end"
  created new head

merge them (from the rename side)

  $ hg merge 'desc("make a executable")'
  merging z and a to z
  0 files updated, 1 files merged, 0 files removed, 0 files unresolved
  (branch merge, don't forget to commit)
  $ hg st --copies
  M z
    a
  $ [ -x z ] || echo "executable bit lost"

merge them (from the chmod side)

  $ hg up -C 'desc("make a executable")'
  1 files updated, 0 files merged, 1 files removed, 0 files unresolved
  $ hg merge 'desc("rename a to z")'
  merging a and z to z
  0 files updated, 1 files merged, 0 files removed, 0 files unresolved
  (branch merge, don't forget to commit)
  $ hg st --copies
  M z
    a
  R a
  $ [ -x z ] || echo "executable bit lost"

  $ cd ..

Removing the flag
-----------------

  $ hg clone base-exec rename+mod-merge-repo-removal
  updating to branch default
  2 files updated, 0 files merged, 0 files removed, 0 files unresolved
  $ cd rename+mod-merge-repo-removal

make "a" non-executable on one side

  $ chmod -x a
  $ cat << EOF > a
  > 1
  > x
  > 3
  > 4
  > 5
  > 6
  > 7
  > 8
  > 9
  > EOF
  $ hg status
  M a
  $ hg ci -m "make a non-executable, and change start"
  $ [ -x z ] && echo "executable bit not removed"
  [1]
  $ hg up ".^"
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved

make "a" renamed on the other side

  $ hg mv a z
  $ hg st --copies
  A z
    a
  R a
  $ cat << EOF > z
  > 1
  > 2
  > 3
  > 4
  > 5
  > 6
  > 7
  > x
  > 9
  > EOF
  $ hg ci -m "rename a to z, and change end"
  created new head

merge them (from the rename side)

  $ hg merge 'desc("make a non-executable")'
  merging z and a to z
  0 files updated, 1 files merged, 0 files removed, 0 files unresolved
  (branch merge, don't forget to commit)
  $ hg st --copies
  M z
    a
  $ [ -x z ] && echo "executable bit not removed"
  [1]

merge them (from the chmod side)

  $ hg up -C 'desc("make a non-executable")'
  1 files updated, 0 files merged, 1 files removed, 0 files unresolved
  $ hg merge 'desc("rename a to z")'
  merging a and z to z
  0 files updated, 1 files merged, 0 files removed, 0 files unresolved
  (branch merge, don't forget to commit)
  $ hg st --copies
  M z
    a
  R a
  $ [ -x z ] && echo "executable bit not removed"
  [1]

  $ cd ..