tests/test-nointerrupt.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 no-windows no-rhg

XXX-RHG this test hangs if `hg` is really `rhg`. This was hidden by the use of
`alias hg=rhg` by run-tests.py. With such alias removed, this test is revealed
buggy. This need to be resolved sooner than later.

Dummy extension simulating unsafe long running command
  $ SYNC_FILE="$TESTTMP/sync-file"
  $ export SYNC_FILE
  $ DONE_FILE="$TESTTMP/done-file"
  $ export DONE_FILE
  $ 
  $ cat > wait_ext.py <<EOF
  > import os
  > import time
  > 
  > from mercurial.i18n import _
  > from mercurial import registrar
  > from mercurial import testing
  > 
  > cmdtable = {}
  > command = registrar.command(cmdtable)
  > 
  > @command(b'wait-signal', [], _(b'SYNC_FILE DONE_FILE'), norepo=True)
  > def sleep(ui, sync_file=b"$SYNC_FILE", done_file=b"$DONE_FILE", **opts):
  >     start = time.time()
  >     with ui.uninterruptible():
  >         testing.write_file(sync_file, b'%d' % os.getpid())
  >         testing.wait_file(done_file)
  >         # make sure we get rescheduled and the signal get a chance to be handled
  >         time.sleep(0.1)
  >         ui.warn(b"end of unsafe operation\n")
  >     ui.warn(b"%d second(s) passed\n" % int(time.time() - start))
  > EOF

  $ cat > send-signal.sh << EOF
  > #!/bin/sh
  > SIG=\$1
  > if [ -z "\$SIG" ]; then
  >    echo "send-signal.sh requires one argument" >&2
  >    exit 1
  > fi
  > "$RUNTESTDIR/testlib/wait-on-file" 10 "$SYNC_FILE" || exit 2
  > kill -s \$SIG \`cat "$SYNC_FILE"\`
  > sleep 1
  > touch "$DONE_FILE"
  > EOF

#if no-windows
  $ chmod +x send-signal.sh
#endif

Kludge to emulate timeout(1) which is not generally available.

Set up repository
  $ hg init repo
  $ cd repo
  $ cat >> $HGRCPATH << EOF
  > [extensions]
  > wait_ext = $TESTTMP/wait_ext.py
  > EOF


Test ctrl-c
  $ rm -f $SYNC_FILE $DONE_FILE
  $ sh -c "../send-signal.sh INT" &
  $ hg wait-signal
  interrupted!
  [255]

  $ cat >> $HGRCPATH << EOF
  > [experimental]
  > nointerrupt = yes
  > EOF

  $ rm -f $SYNC_FILE $DONE_FILE
  $ sh -c "../send-signal.sh INT" &
  $ hg wait-signal
  interrupted!
  [255]

  $ cat >> $HGRCPATH << EOF
  > [experimental]
  > nointerrupt-interactiveonly = False
  > EOF

  $ rm -f $SYNC_FILE $DONE_FILE
  $ sh -c "../send-signal.sh INT" &
  $ hg wait-signal
  shutting down cleanly
  press ^C again to terminate immediately (dangerous)
  end of unsafe operation
  interrupted!
  [255]