tests/test-revset-outgoing.t

scmutil: add file object wrapper class to check ambiguity at closing

In Mercurial source tree, opening a file in "a"/"a+" mode like below
doesn't specify atomictemp=True for vfs, and this avoids file stat
ambiguity check by atomictempfile.

  - writing changes out in revlog layer uses "a+" mode
  - truncation in repair.strip() uses "a" mode
  - truncation in transaction._playback() uses "a" mode

If steps below occurs at "the same time in sec", all of mtime, ctime
and size are same between (1) and (3).

  1. append data to revlog-style file (and close transaction)
  2. discard appended data by truncation (strip or rollback)
  3. append same size but different data to revlog-style file again

Therefore, cache validation doesn't work after (3) as expected.

This patch adds file object wrapper class checkambigatclosing to check
(and get rid of) ambiguity at closing. It is used by vfs in subsequent
patch.

This is a part of ExactCacheValidationPlan.

    https://www.mercurial-scm.org/wiki/ExactCacheValidationPlan

BTW, checkambigatclosing is tested in test-filecache.py, even though
it doesn't use filecache itself, because filecache assumes that file
stat ambiguity never occurs (and there is no another test-*.py related
to filecache).

  $ cat >> $HGRCPATH <<EOF
  > [alias]
  > tlog = log --template "{rev}:{node|short}: '{desc}' {branches}\n"
  > tglog = tlog -G
  > tout = out --template "{rev}:{node|short}: '{desc}' {branches}\n"
  > EOF

  $ hg init a
  $ cd a

  $ echo a > a
  $ hg ci -Aqm0

  $ echo foo >> a
  $ hg ci -Aqm1

  $ hg up -q 0

  $ hg branch stable
  marked working directory as branch stable
  (branches are permanent and global, did you want a bookmark?)
  $ echo bar >> a
  $ hg ci -qm2

  $ hg tglog
  @  2:7bee6c3bea3a: '2' stable
  |
  | o  1:3560197d8331: '1'
  |/
  o  0:f7b1eb17ad24: '0'
  

  $ cd ..

  $ hg clone -q a#stable b

  $ cd b
  $ cat .hg/hgrc
  # example repository config (see 'hg help config' for more info)
  [paths]
  default = $TESTTMP/a#stable (glob)
  
  # path aliases to other clones of this repo in URLs or filesystem paths
  # (see 'hg help config.paths' for more info)
  #
  # default-push = ssh://[e-mail]/hg/jdoes-fork
  # my-fork      = ssh://[e-mail]/hg/jdoes-fork
  # my-clone     = /home/jdoe/jdoes-clone
  
  [ui]
  # name and email (local to this repository, optional), e.g.
  # username = Jane Doe <[e-mail]>

  $ echo red >> a
  $ hg ci -qm3

  $ hg up -q default

  $ echo blue >> a
  $ hg ci -qm4

  $ hg tglog
  @  3:f0461977a3db: '4'
  |
  | o  2:1d4099801a4e: '3' stable
  | |
  | o  1:7bee6c3bea3a: '2' stable
  |/
  o  0:f7b1eb17ad24: '0'
  

  $ hg tout
  comparing with $TESTTMP/a (glob)
  searching for changes
  2:1d4099801a4e: '3' stable

  $ hg tlog -r 'outgoing()'
  2:1d4099801a4e: '3' stable

  $ hg tout ../a#default
  comparing with ../a
  searching for changes
  3:f0461977a3db: '4' 

  $ hg tlog -r 'outgoing("../a#default")'
  3:f0461977a3db: '4' 

  $ echo "green = ../a#default" >> .hg/hgrc

  $ cat .hg/hgrc
  # example repository config (see 'hg help config' for more info)
  [paths]
  default = $TESTTMP/a#stable (glob)
  
  # path aliases to other clones of this repo in URLs or filesystem paths
  # (see 'hg help config.paths' for more info)
  #
  # default-push = ssh://[e-mail]/hg/jdoes-fork
  # my-fork      = ssh://[e-mail]/hg/jdoes-fork
  # my-clone     = /home/jdoe/jdoes-clone
  
  [ui]
  # name and email (local to this repository, optional), e.g.
  # username = Jane Doe <[e-mail]>
  green = ../a#default

  $ hg tout green
  comparing with green
  abort: repository green not found!
  [255]

  $ hg tlog -r 'outgoing("green")'
  abort: repository green not found!
  [255]

  $ cd ..