view tests/test-transaction-safety.t @ 48507:58a3be48ddd2

simplemerge: stop merging file flags

As 384df4db6520 (merge: merge file flags together with file content,
2013-01-09) explains, we shouldn't do a 3-way merge of the
symlink. However, since 84614212ae39 (flags: actually merge flags in
simplemerge, 2020-05-16), we do that in
`simplemerge.simplemerge()`. What's more, the merging of the
executable flag there isn't actually necessary; it was made a no-op by
the very next commit, i.e. 4234c9af515d (flags: read flag from
dirstate/disk for workingcopyctx (issue5743), 2020-05-16).

I found the overall flag-merging code (not the bit in
`simplemerge.py`) very hard to follow, but I think I now finally
understand how it works. `mergestate.resolve()` calculates the merged
file flags and sets them on the local side of the merge (confusingly
by calling `_restore_backup()`). Then it calls
`filemerge.filemerge()`, which in turn calls
`simplemerge.simplemerge()` (if premerge is enabled). That means that
the flags on the local side `fcs.flags()` are already correct when the
flag-merging code in `simplemerge.simplemerge()` runs. Interestingly,
that code still works when the local side already has the merged
value, it just doesn't change the value. Here's a truth table to
explain why:

```
BLOMCAR
0000000
0011111
0101011
0111111
1000000
1010000
1100000
1111101
```

B: Base
L: Local
O: Other
M: Merged flags from `mergestate.resolve()`, i.e. what's called "local"
   when we get to `simplemerge.simplemerge()`
C: `commonflags` in `simplemerge.simplemerge()`, i.e. `M & O`
A: `addedflags` in `simplemerge.simplemerge()`, i.e. `(M ^ O) - B`
R: Re-merged flags `simplemerge.simplemerge()`, i.e. `C | A`

As you can see, the re-merged flags are always unchanged compared to
the initial merged flags (R equals M).

Therefore, this patch effectively backs out 84614212ae39. (I might
later refactor this code to have the flags explicitly passed in.)

`simplemerge.simplemerge()` is also called from
`contrib/simplemerge.py`, but that code never passes any flags.

Differential Revision: https://phab.mercurial-scm.org/D11879

Test transaction safety
=======================

#testcases revlogv1 revlogv2 changelogv2

#if revlogv1

  $ cat << EOF >> $HGRCPATH
  > [experimental]
  > revlogv2=no
  > EOF

#endif

#if revlogv2

  $ cat << EOF >> $HGRCPATH
  > [experimental]
  > revlogv2=enable-unstable-format-and-corrupt-my-data
  > EOF

#endif

#if changelogv2

  $ cat << EOF >> $HGRCPATH
  > [format]
  > exp-use-changelog-v2=enable-unstable-format-and-corrupt-my-data
  > EOF

#endif

This test basic case to make sure external process do not see transaction
content until it is committed.

# TODO: also add an external reader accessing revlog files while they are written
#       (instead of during transaction finalisation)

# TODO: also add stream clone and hardlink clone happening during these transaction.

setup
-----

synchronisation+output script using the following schedule:

[A1] "external"       is started
[A2] "external"       waits on EXT_UNLOCK
[A2] "external"       + creates EXT_WAITING → unlocks [C1]
[B1] "hg commit/pull" is started
[B2] "hg commit/pull" is ready to be committed
[B3] "hg commit/pull" spawn "internal" using a pretxnclose hook (need [C4])
[C1] "internal"       waits on EXT_WAITING (need [A2])
[C2] "internal"       creates EXT_UNLOCK → unlocks [A2]
[C3] "internal"       show the tipmost revision (inside of the transaction)
[C4] "internal"       waits on EXT_DONE (need [A4])
[A3] "external"       show the tipmost revision (outside of the transaction)
[A4] "external"       creates EXT_DONE → unlocks [C4]
[C5] "internal"       end of execution -> unlock [B3]
[B4] "hg commit/pull" transaction is committed on disk


  $ mkdir sync
  $ mkdir output
  $ mkdir script
  $ HG_TEST_FILE_EXT_WAITING=$TESTTMP/sync/ext_waiting
  $ export HG_TEST_FILE_EXT_WAITING
  $ HG_TEST_FILE_EXT_UNLOCK=$TESTTMP/sync/ext_unlock
  $ export HG_TEST_FILE_EXT_UNLOCK
  $ HG_TEST_FILE_EXT_DONE=$TESTTMP/sync/ext_done
  $ export HG_TEST_FILE_EXT_DONE
  $ cat << EOF > script/external.sh
  > #!/bin/sh
  > "$RUNTESTDIR/testlib/wait-on-file" 5 "$HG_TEST_FILE_EXT_UNLOCK" "$HG_TEST_FILE_EXT_WAITING"
  > hg log --rev 'tip' -T 'external: {rev} {desc}\n' > "$TESTTMP/output/external.out"
  > touch "$HG_TEST_FILE_EXT_DONE"
  > EOF
  $ cat << EOF > script/internal.sh
  > #!/bin/sh
  > "$RUNTESTDIR/testlib/wait-on-file" 5 "$HG_TEST_FILE_EXT_WAITING"
  > touch "$HG_TEST_FILE_EXT_UNLOCK"
  > hg log --rev 'tip' -T 'internal: {rev} {desc}\n' > "$TESTTMP/output/internal.out"
  > "$RUNTESTDIR/testlib/wait-on-file" 5 "$HG_TEST_FILE_EXT_DONE"
  > EOF


Automated commands:

  $ make_one_commit() {
  > rm -f $TESTTMP/sync/*
  > rm -f $TESTTMP/output/*
  > hg log --rev 'tip' -T 'pre-commit: {rev} {desc}\n'
  > echo x >> a
  > sh $TESTTMP/script/external.sh & hg commit -m "$1"
  > cat $TESTTMP/output/external.out
  > cat $TESTTMP/output/internal.out
  > hg log --rev 'tip' -T 'post-tr:  {rev} {desc}\n'
  > }


  $ make_one_pull() {
  > rm -f $TESTTMP/sync/*
  > rm -f $TESTTMP/output/*
  > hg log --rev 'tip' -T 'pre-commit: {rev} {desc}\n'
  > echo x >> a
  > sh $TESTTMP/script/external.sh & hg pull ../other-repo/ --rev "$1" --force --quiet
  > cat $TESTTMP/output/external.out
  > cat $TESTTMP/output/internal.out
  > hg log --rev 'tip' -T 'post-tr:  {rev} {desc}\n'
  > }

prepare a large source to which to pull from:

The source is large to unsure we don't use inline more after the pull

  $ hg init other-repo
  $ hg -R other-repo debugbuilddag .+500


prepare an empty repository where to make test:

  $ hg init repo
  $ cd repo
  $ touch a
  $ hg add a

prepare a small extension to controll inline size

  $ mkdir $TESTTMP/ext
  $ cat << EOF > $TESTTMP/ext/small_inline.py
  > from mercurial import revlog
  > revlog._maxinline = 64 * 100
  > EOF




  $ cat << EOF >> $HGRCPATH
  > [extensions]
  > small_inline=$TESTTMP/ext/small_inline.py
  > [hooks]
  > pretxnclose = sh $TESTTMP/script/internal.sh
  > EOF

check this is true for the initial commit (inline → inline)
-----------------------------------------------------------

the repository should still be inline (for relevant format)

  $ make_one_commit first
  pre-commit: -1 
  external: -1 
  internal: 0 first
  post-tr:  0 first

#if revlogv1

  $ hg debugrevlog -c | grep inline
  flags  : inline

#endif

check this is true for extra commit (inline → inline)
-----------------------------------------------------

the repository should still be inline (for relevant format)

#if revlogv1

  $ hg debugrevlog -c | grep inline
  flags  : inline

#endif

  $ make_one_commit second
  pre-commit: 0 first
  external: 0 first
  internal: 1 second
  post-tr:  1 second

#if revlogv1

  $ hg debugrevlog -c | grep inline
  flags  : inline

#endif

check this is true for a small pull (inline → inline)
-----------------------------------------------------

the repository should still be inline (for relevant format)

#if revlogv1

  $ hg debugrevlog -c | grep inline
  flags  : inline

#endif

  $ make_one_pull 3
  pre-commit: 1 second
  warning: repository is unrelated
  external: 1 second
  internal: 5 r3
  post-tr:  5 r3

#if revlogv1

  $ hg debugrevlog -c | grep inline
  flags  : inline

#endif

Make a large pull (inline → no-inline)
---------------------------------------

the repository should no longer be inline (for relevant format)

#if revlogv1

  $ hg debugrevlog -c | grep inline
  flags  : inline

#endif

  $ make_one_pull 400
  pre-commit: 5 r3
  external: 5 r3
  internal: 402 r400
  post-tr:  402 r400

#if revlogv1

  $ hg debugrevlog -c | grep inline
  [1]

#endif

check this is true for extra commit (no-inline → no-inline)
-----------------------------------------------------------

the repository should no longer be inline (for relevant format)

#if revlogv1

  $ hg debugrevlog -c | grep inline
  [1]

#endif

  $ make_one_commit third
  pre-commit: 402 r400
  external: 402 r400
  internal: 403 third
  post-tr:  403 third

#if revlogv1

  $ hg debugrevlog -c | grep inline
  [1]

#endif


Make a  pull (not-inline → no-inline)
-------------------------------------

the repository should no longer be inline (for relevant format)

#if revlogv1

  $ hg debugrevlog -c | grep inline
  [1]

#endif

  $ make_one_pull tip
  pre-commit: 403 third
  external: 403 third
  internal: 503 r500
  post-tr:  503 r500

#if revlogv1

  $ hg debugrevlog -c | grep inline
  [1]

#endif