tests/test-check-shbang.t

rust-revlog: fix RevlogEntry.data() for NULL_REVISION

Before this change, the pseudo-entry returned by `Revlog.get_entry` for
`NULL_REVISION` would trigger errors in application code using it.

For example, this fixes a crash spotted with changelog data
while implementing RHGitaly: `Changelog.data_for_rev(-1)` was already
returning the pseudo content as expected, e.g., for `hg log`, but
`Changelog.entry_for_rev(-1).data()` would still crash with
"corrupted revlog, hash check failed for revision -1". There is
an added test for this scenario.

#require test-repo

  $ . "$TESTDIR/helpers-testrepo.sh"
  $ cd "`dirname "$TESTDIR"`"

look for python scripts that do not use /usr/bin/env

  $ testrepohg files 'set:grep(r"^#!.*?python") and not grep(r"^#!/usr/bi{1}n/env python") - **/*.t'
  [1]

In tests, enforce $PYTHON and *not* /usr/bin/env python or similar:
  $ testrepohg files 'set:grep(r"#!.*?python") and **/*.t' \
  > -X tests/test-check-execute.t \
  > -X tests/test-check-format.t \
  > -X tests/test-check-module-imports.t \
  > -X tests/test-check-pyflakes.t \
  > -X tests/test-check-shbang.t \
  > -X tests/test-highlight.t
  [1]

The above exclusions are because they're looking for files that
contain Python but don't end in .py - please avoid adding more.

look for shell scripts that do not use /bin/sh

  $ testrepohg files 'set:grep(r"^#!.*/bi{1}n/sh") and not grep(r"^#!/bi{1}n/sh")'
  [1]