project: use os.rename() instead of shutil.move() for cloned manifest

As reported in zephyrproject-rtos#963 (thanks!) and seen in the source of
https://github.com/python/cpython/blob/main/Lib/shutil.py,
`shutil.move()` tries an (atomic) `os.rename()` first, then falls back
on a copy+delete in case of an OSError raised by `os.rename()`. The
source and destination being on different filesystems is one of the (too
many?) conditions caught by this OSError and how `shutil.move()` claims
to "optimize" moves on the same filesystem thanks to
`os.rename()`. Maybe there isn't another, simple and reliable way to
check whether source and destionation are on the same filesystem and
perform this optimization?

In this particular `project.py` use case however, we _know_ that both
are on the same filesystem because we purposely located them in the same
directory so we can benefit from very fast and atomic renames guaranteed
by practically all filesystems in the universe. So, let's simplify
`shutil.move()` down to `os.rename()` in this particular case. Quoting
the same `Lib/shutil.py#move()` source:

    os.rename() is preferably used if the source and destination are on the
    same filesystem. [...]
    It's recommended to use os.rename() if atomic move is strictly required.

But wait... if we know we are always on the same filesystem, then why
does this even matter? os.rename() should always succeed inside
shutil.move() and this minor cleanup should never make any visible
difference, right? To answer that we need to go back to zephyrproject-rtos#963, NTFS and
antivirus scanners which when combined together can break even the
simplest things like renaming a directory. While this simplification is
far from making west compatible with such utterly broken systems, it
does remove a lot of complexity and headaches when such a failure
happens and it recommends the existing --rename-delay workaround.

Signed-off-by: Marc Herbert <Marc.Herbert@gmail.com>

Author: marc-hb

src/west/app/project.py

@@ -516,18 +516,16 @@ def bootstrap(self, args) -> Path:
 
         self.dbg('moving', tempdir, 'to', manifest_abspath, level=Verbosity.DBG_EXTREME)
 
-        # As shutil.move() is used to relocate tempdir, if manifest_abspath
-        # is an existing directory, tmpdir will be moved _inside_ it, instead
-        # of _to_ that path - this must be avoided. If manifest_abspath exists
-        # but is not a directory, then semantics depend on os.rename(), so
-        # avoid that too...
+        # If manifest_abspath exists but is not a directory, then semantics
+        # depend on os.rename(), so avoid that
         if manifest_abspath.exists():
             self.die(f'target directory already exists ({manifest_abspath})')
 
         manifest_abspath.parent.mkdir(parents=True, exist_ok=True)
         try:
-            shutil.move(os.fspath(tempdir), os.fspath(manifest_abspath))
-        except shutil.Error as e:
+            os.rename(os.fspath(tempdir), os.fspath(manifest_abspath))
+        except OSError as e:
+            self.err("try west init --rename-delay; see west init -h")
             self.die(e)
         self.small_banner('setting manifest.path to', manifest_path)
         self.config = Configuration(topdir=topdir)