tests/test-lock-badness.t

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

#require unix-permissions no-root no-windows

Prepare

  $ hg init a
  $ echo a > a/a
  $ hg -R a ci -A -m a
  adding a

  $ hg clone a b
  updating to branch default
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved

Test that raising an exception in the release function doesn't cause the lock to choke

  $ cat > testlock.py << EOF
  > from mercurial import error, registrar
  > 
  > cmdtable = {}
  > command = registrar.command(cmdtable)
  > 
  > def acquiretestlock(repo, releaseexc):
  >     def unlock():
  >         if releaseexc:
  >             raise error.Abort(b'expected release exception')
  >     l = repo._lock(repo.vfs, b'testlock', False, unlock, None, b'test lock')
  >     return l
  > 
  > @command(b'testlockexc')
  > def testlockexc(ui, repo):
  >     testlock = acquiretestlock(repo, True)
  >     try:
  >         testlock.release()
  >     finally:
  >         try:
  >             testlock = acquiretestlock(repo, False)
  >         except error.LockHeld:
  >             raise error.Abort(b'lockfile on disk even after releasing!')
  >         testlock.release()
  > EOF
  $ cat >> $HGRCPATH << EOF
  > [extensions]
  > testlock=$TESTTMP/testlock.py
  > EOF

  $ hg -R b testlockexc
  abort: expected release exception
  [255]

One process waiting for another

  $ cat > hooks.py << EOF
  > import time
  > def sleepone(**x): time.sleep(1)
  > def sleephalf(**x): time.sleep(0.5)
  > EOF
  $ echo b > b/b
  $ hg -R b ci -A -m b --config hooks.precommit="python:`pwd`/hooks.py:sleepone" > stdout &
  $ hg -R b up -q --config ui.timeout.warn=0 --config hooks.pre-update="python:`pwd`/hooks.py:sleephalf" \
  > > preup-stdout 2>preup-stderr
  $ wait
  $ cat preup-stdout
  $ cat preup-stderr
  waiting for lock on working directory of b held by process '*' on host '*' (glob)
  got lock after * seconds (glob)
  $ cat stdout
  adding b

On processs waiting on another, warning after a long time.

  $ echo b > b/c
  $ hg -R b ci -A -m b --config hooks.precommit="python:`pwd`/hooks.py:sleepone" > stdout &
  $ hg -R b up -q --config hooks.pre-update="python:`pwd`/hooks.py:sleephalf" \
  > --config ui.timeout.warn=250 \
  > > preup-stdout 2>preup-stderr
  $ wait
  $ cat preup-stdout
  $ cat preup-stderr
  $ cat stdout
  adding c

On processs waiting on another, warning disabled.

  $ echo b > b/d
  $ hg -R b ci -A -m b --config hooks.precommit="python:`pwd`/hooks.py:sleepone" > stdout &
  $ hg -R b up -q --config hooks.pre-update="python:`pwd`/hooks.py:sleephalf" \
  > --config ui.timeout.warn=-1 \
  > > preup-stdout 2>preup-stderr
  $ wait
  $ cat preup-stdout
  $ cat preup-stderr
  $ cat stdout
  adding d

check we still print debug output

On processs waiting on another, warning after a long time (debug output on)

  $ echo b > b/e
  $ hg -R b ci -A -m b --config hooks.precommit="python:`pwd`/hooks.py:sleepone" > stdout &
  $ hg -R b up --config hooks.pre-update="python:`pwd`/hooks.py:sleephalf" \
  > --config ui.timeout.warn=250 --debug\
  > > preup-stdout 2>preup-stderr
  $ wait
  $ cat preup-stdout
  calling hook pre-update: hghook_pre-update.sleephalf
  waiting for lock on working directory of b held by process '*' on host '*' (glob)
  got lock after * seconds (glob)
  0 files updated, 0 files merged, 0 files removed, 0 files unresolved
  $ cat preup-stderr
  $ cat stdout
  adding e

On processs waiting on another, warning disabled, (debug output on)

  $ echo b > b/f
  $ hg -R b ci -A -m b --config hooks.precommit="python:`pwd`/hooks.py:sleepone" > stdout &
  $ hg -R b up --config hooks.pre-update="python:`pwd`/hooks.py:sleephalf" \
  > --config ui.timeout.warn=-1 --debug\
  > > preup-stdout 2>preup-stderr
  $ wait
  $ cat preup-stdout
  calling hook pre-update: hghook_pre-update.sleephalf
  waiting for lock on working directory of b held by process '*' on host '*' (glob)
  got lock after * seconds (glob)
  0 files updated, 0 files merged, 0 files removed, 0 files unresolved
  $ cat preup-stderr
  $ cat stdout
  adding f

Pushing to a local read-only repo that can't be locked

  $ chmod 100 a/.hg/store

  $ hg -R b push a
  pushing to a
  searching for changes
  abort: could not lock repository a: Permission denied
  [20]

  $ chmod 700 a/.hg/store