tests/test-install.t

dirstate: make writing in-memory changes aware of transaction activity

This patch delays writing in-memory changes out, if transaction is
running.

'_getfsnow()' is defined as a function, to hook it easily for
ambiguous timestamp tests (see also fakedirstatewritetime.py)

'if tr:' code path in this patch is still disabled at this revision,
because there is no client invoking 'dirstate.write()' with repo
object.

BTW, this patch changes 'dirstate.invalidate()' semantics around
'dirstate.write()' in a transaction scope:

  before:
    with repo.transaction():
        dirstate.CHANGE('A')
        dirstate.write() # change for A is written out here
        dirstate.CHANGE('B')
        dirstate.invalidate() # discards only change for B

  after:
    with repo.transaction():
        dirstate.CHANGE('A')
        dirstate.write() # change for A is still kept in memory
        dirstate.CHANGE('B')
        dirstate.invalidate() # discards changes for A and B

Fortunately, there is no code path expecting the former, at least, in
Mercurial itself, because 'dirstateguard' was introduced to remove
such 'dirstate.invalidate()'.

hg debuginstall
  $ hg debuginstall
  checking encoding (ascii)...
  checking Python executable (*) (glob)
  checking Python version (2.*) (glob)
  checking Python lib (*lib*)... (glob)
  checking installed modules (*mercurial)... (glob)
  checking templates (*mercurial?templates)... (glob)
  checking commit editor...
  checking username...
  no problems detected

hg debuginstall with no username
  $ HGUSER= hg debuginstall
  checking encoding (ascii)...
  checking Python executable (*) (glob)
  checking Python version (2.*) (glob)
  checking Python lib (*lib*)... (glob)
  checking installed modules (*mercurial)... (glob)
  checking templates (*mercurial?templates)... (glob)
  checking commit editor...
  checking username...
   no username supplied
   (specify a username in your configuration file)
  1 problems detected, please check your install!
  [1]

path variables are expanded (~ is the same as $TESTTMP)
  $ mkdir tools
  $ touch tools/testeditor.exe
#if execbit
  $ chmod 755 tools/testeditor.exe
#endif
  $ hg debuginstall --config ui.editor=~/tools/testeditor.exe
  checking encoding (ascii)...
  checking Python executable (*) (glob)
  checking Python version (*) (glob)
  checking Python lib (*lib*)... (glob)
  checking installed modules (*mercurial)... (glob)
  checking templates (*mercurial?templates)... (glob)
  checking commit editor...
  checking username...
  no problems detected