tests/test-dirstate.t

posix: always seek to EOF when opening a file in append mode

Python 3 already does this, so skip it there.

Consider the program:

   #include <stdio.h>

   int main() {
     FILE *f = fopen("narf", "w");
     fprintf(f, "narf\n");
     fclose(f);

     f = fopen("narf", "a");
     printf("%ld\n", ftell(f));
     fprintf(f, "troz\n");
     printf("%ld\n", ftell(f));

     return 0;
   }

on macOS, FreeBSD, and Linux with glibc, this program prints

   5
   10

but on musl libc (Alpine Linux and probably others) this prints

   0
   10

By my reading of
https://pubs.opengroup.org/onlinepubs/009695399/functions/fopen.html
this is technically correct, specifically:

> Opening a file with append mode (a as the first character in the
> mode argument) shall cause all subsequent writes to the file to be
> forced to the then current end-of-file, regardless of intervening
> calls to fseek().

in other words, the file position doesn't really matter in append-mode
files, and we can't depend on it being at all meaningful unless we
perform a seek() before tell() after open(..., 'a'). Experimentally
after a .write() we can do a .tell() and it'll always be reasonable,
but I'm unclear from reading the specification if that's a smart thing
to rely on. This matches what we do on Windows and what Python 3 does
for free, so let's just be consistent. Thanks to Yuya for the idea.

------ Test dirstate._dirs refcounting

  $ hg init t
  $ cd t
  $ mkdir -p a/b/c/d
  $ touch a/b/c/d/x
  $ touch a/b/c/d/y
  $ touch a/b/c/d/z
  $ hg ci -Am m
  adding a/b/c/d/x
  adding a/b/c/d/y
  adding a/b/c/d/z
  $ hg mv a z
  moving a/b/c/d/x to z/b/c/d/x
  moving a/b/c/d/y to z/b/c/d/y
  moving a/b/c/d/z to z/b/c/d/z

Test name collisions

  $ rm z/b/c/d/x
  $ mkdir z/b/c/d/x
  $ touch z/b/c/d/x/y
  $ hg add z/b/c/d/x/y
  abort: file 'z/b/c/d/x' in dirstate clashes with 'z/b/c/d/x/y'
  [255]
  $ rm -rf z/b/c/d
  $ touch z/b/c/d
  $ hg add z/b/c/d
  abort: directory 'z/b/c/d' already in dirstate
  [255]

  $ cd ..

Issue1790: dirstate entry locked into unset if file mtime is set into
the future

Prepare test repo:

  $ hg init u
  $ cd u
  $ echo a > a
  $ hg add
  adding a
  $ hg ci -m1

Set mtime of a into the future:

  $ touch -t 202101011200 a

Status must not set a's entry to unset (issue1790):

  $ hg status
  $ hg debugstate
  n 644          2 2021-01-01 12:00:00 a

Test modulo storage/comparison of absurd dates:

#if no-aix
  $ touch -t 195001011200 a
  $ hg st
  $ hg debugstate
  n 644          2 2018-01-19 15:14:08 a
#endif

Verify that exceptions during a dirstate change leave the dirstate
coherent (issue4353)

  $ cat > ../dirstateexception.py <<EOF
  > from __future__ import absolute_import
  > from mercurial import (
  >   error,
  >   extensions,
  >   merge,
  > )
  > 
  > def wraprecordupdates(orig, repo, actions, branchmerge):
  >     raise error.Abort("simulated error while recording dirstateupdates")
  > 
  > def reposetup(ui, repo):
  >     extensions.wrapfunction(merge, 'recordupdates', wraprecordupdates)
  > EOF

  $ hg rm a
  $ hg commit -m 'rm a'
  $ echo "[extensions]" >> .hg/hgrc
  $ echo "dirstateex=../dirstateexception.py" >> .hg/hgrc
  $ hg up 0
  abort: simulated error while recording dirstateupdates
  [255]
  $ hg log -r . -T '{rev}\n'
  1
  $ hg status
  ? a