tests/test-histedit-no-backup.t

make: switch the PYTHON default to `py.exe -3` on Windows

Python3 _is_ named `python.exe` on Windows, but that isn't necessarily on PATH
when installing from python.org.  I do happen to have a python.exe on PATH in
`$LOCALAPPDATA/Microsoft/WindowsApps`, but it appears to be 0 bytes (likely
because of permission issues), and doesn't run:

    $ python -V
     - Cannot open

Pulkit hit the same error as I did though, so it isn't just my system:

    $ make -C . local
    make: Entering directory `/home/Dell/repos/hg-committed`
    python setup.py  \
              build_py -c -d . \
              build_ext  -i \
              build_hgexe  -i \
              build_mo
     - Cannot openmake: *** [local] Error 1

The `py.exe` dispatcher lives in the Windows directory (so it is on PATH), looks
up the python.org installation, and invokes that interpreter directly.  I get a
warning with py39, but if it's our issue, it was an existing one:

    $ make -C .. local
    make: Entering directory `/c/Users/Matt/hg'
    py -3 setup.py  \
              build_py -c -d . \
              build_ext  -i \
              build_hgexe  -i \
              build_mo
    C:\Users\Matt\AppData\Local\Programs\Python\Python39\lib\site-packages\setuptools\distutils_patch.py:25:
        UserWarning: Distutils was imported before Setuptools. This usage is discouraged and may
        exhibit undesirable behaviors or errors. Please use Setuptools' objects directly or at least
        import Setuptools first.
      warnings.warn(

The end result is a py3 based hg.exe that annoyingly won't run because it can't
find python39.dll.  It will run tests (the ones without the `python3` shbang
line anyway), because the test runner adjusts PATH to include the python running
it.

Differential Revision: https://phab.mercurial-scm.org/D9361

#testcases abortcommand abortflag

#if abortflag
  $ cat >> $HGRCPATH <<EOF
  > [alias]
  > abort = histedit --abort
  > EOF
#endif

  $ . "$TESTDIR/histedit-helpers.sh"

Enable extension used by this test
  $ cat >>$HGRCPATH <<EOF
  > [extensions]
  > histedit=
  > EOF

=================================
Test backup-bundle config option|
=================================
Repo setup:
  $ hg init foo
  $ cd foo
  $ echo first>file
  $ hg ci -qAm one
  $ echo second>>file
  $ hg ci -m two
  $ echo third>>file
  $ hg ci -m three
  $ echo forth>>file
  $ hg ci -m four
  $ hg log -G --style compact
  @  3[tip]   7d5187087c79   1970-01-01 00:00 +0000   test
  |    four
  |
  o  2   80d23dfa866d   1970-01-01 00:00 +0000   test
  |    three
  |
  o  1   6153eb23e623   1970-01-01 00:00 +0000   test
  |    two
  |
  o  0   36b4bdd91f5b   1970-01-01 00:00 +0000   test
       one
  
Test when `backup-bundle` config option is enabled:
  $ hg histedit -r '36b4bdd91f5b' --commands - << EOF
  > pick 36b4bdd91f5b 0 one
  > pick 6153eb23e623 1 two
  > roll 80d23dfa866d 2 three
  > edit 7d5187087c79 3 four
  > EOF
  merging file
  Editing (7d5187087c79), you may commit or record as needed now.
  (hg histedit --continue to resume)
  [240]
  $ hg abort
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved
  saved backup bundle to $TESTTMP/foo/.hg/strip-backup/1d8f701c7b35-cf7be322-backup.hg
  saved backup bundle to $TESTTMP/foo/.hg/strip-backup/5c0056670bce-b54b65d0-backup.hg

Test when `backup-bundle` config option is not enabled
Enable config option:
  $ cat >>$HGRCPATH <<EOF
  > [rewrite]
  > backup-bundle = False
  > EOF

  $ hg histedit -r '36b4bdd91f5b' --commands - << EOF
  > pick 36b4bdd91f5b 0 one
  > pick 6153eb23e623 1 two
  > roll 80d23dfa866d 2 three
  > edit 7d5187087c79 3 four
  > EOF
  merging file
  Editing (7d5187087c79), you may commit or record as needed now.
  (hg histedit --continue to resume)
  [240]

  $ hg abort
  1 files updated, 0 files merged, 0 files removed, 0 files unresolved