tests/test-rhg.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

#require rust

Define an rhg function that will only run if rhg exists
  $ rhg() {
  > if [ -f "$RUNTESTDIR/../rust/target/debug/rhg" ]; then
  >   "$RUNTESTDIR/../rust/target/debug/rhg" "$@"
  > else
  >   echo "skipped: Cannot find rhg. Try to run cargo build in rust/rhg."
  >   exit 80
  > fi
  > }

Unimplemented command
  $ rhg unimplemented-command
  error: Found argument 'unimplemented-command' which wasn't expected, or isn't valid in this context
  
  USAGE:
      rhg <SUBCOMMAND>
  
  For more information try --help
  [252]

Finding root
  $ rhg root
  abort: no repository found in '$TESTTMP' (.hg not found)!
  [255]

  $ hg init repository
  $ cd repository
  $ rhg root
  $TESTTMP/repository

Unwritable file descriptor
  $ rhg root > /dev/full
  abort: No space left on device (os error 28)
  [255]

Deleted repository
  $ rm -rf `pwd`
  $ rhg root
  abort: error getting current working directory: $ENOENT$
  [255]

Listing tracked files
  $ cd $TESTTMP
  $ hg init repository
  $ cd repository
  $ for i in 1 2 3; do
  >   echo $i >> file$i
  >   hg add file$i
  > done
  > hg commit -m "commit $i" -q

Listing tracked files from root
  $ rhg files
  file1
  file2
  file3

Listing tracked files from subdirectory
  $ mkdir -p path/to/directory
  $ cd path/to/directory
  $ rhg files
  ../../../file1
  ../../../file2
  ../../../file3

Listing tracked files through broken pipe
  $ rhg files | head -n 1
  ../../../file1

Debuging data in inline index
  $ cd $TESTTMP
  $ rm -rf repository
  $ hg init repository
  $ cd repository
  $ for i in 1 2 3; do
  >   echo $i >> file$i
  >   hg add file$i
  >   hg commit -m "commit $i" -q
  > done
  $ rhg debugdata -c 2
  e36fa63d37a576b27a69057598351db6ee5746bd
  test
  0 0
  file3
  
  commit 3 (no-eol)
  $ rhg debugdata -m 2
  file1\x00b8e02f6433738021a065f94175c7cd23db5f05be (esc)
  file2\x005d9299349fc01ddd25d0070d149b124d8f10411e (esc)
  file3\x002661d26c649684b482d10f91960cc3db683c38b4 (esc)

Debuging with full node id
  $ rhg debugdata -c `hg log -r 0 -T '{node}'`
  c8e64718e1ca0312eeee0f59d37f8dc612793856
  test
  0 0
  file1
  
  commit 1 (no-eol)

Cat files
  $ cd $TESTTMP
  $ rm -rf repository
  $ hg init repository
  $ cd repository
  $ echo "original content" > original
  $ hg add original
  $ hg commit -m "add original" original
  $ rhg cat -r 0 original
  original content
Cat copied file should not display copy metadata
  $ hg copy original copy_of_original
  $ hg commit -m "add copy of original"
  $ rhg cat -r 1 copy_of_original
  original content