tests/test-debian-packages.t

tests: add test for Rust formatting

We enforce formatting for Python and C. It makes sense to do it
for Rust as well.

Since our rustfmt.toml relies on unstable rustfmt features, we
need to use a Nightly rustfmt with --unstable-features in order
for it to work. This is a bit hacky and I would prefer we remove
this requirement. But for now, this commit assumes this is the
way things must be and we go out of our way to detect and use the
rustfmt from the "nightly" toolchain, as installed via rustup.

We had to add some environment variables to the tests to make
the Rust binaries happy. Otherwise when running rustfmt we get
an error about no default toolchain being installed.

Differential Revision: https://phab.mercurial-scm.org/D7579

#require test-repo slow debhelper debdeps

  $ . "$TESTDIR/helpers-testrepo.sh"
  $ testrepohgenv

Ensure debuild doesn't run the testsuite, as that could get silly.
  $ DEB_BUILD_OPTIONS=nocheck
  $ export DEB_BUILD_OPTIONS
  $ OUTPUTDIR=`pwd`
  $ export OUTPUTDIR

  $ cd "$TESTDIR"/..
  $ make deb > $OUTPUTDIR/build.log 2>&1
  $ cd $OUTPUTDIR
  $ ls *.deb | grep -v 'dbg'
  mercurial_*.deb (glob)
should have .so and .py
  $ dpkg --contents mercurial_*.deb | egrep '(localrepo|parsers)'
  * ./usr/lib/python3/dist-packages/mercurial/cext/parsers*.so (glob)
  * ./usr/lib/python3/dist-packages/mercurial/localrepo.py (glob)
  * ./usr/lib/python3/dist-packages/mercurial/pure/parsers.py (glob)
should have zsh completions
  $ dpkg --contents mercurial_*.deb | egrep 'zsh.*[^/]$'
  * ./usr/share/zsh/vendor-completions/_hg (glob)
should have chg
  $ dpkg --contents mercurial_*.deb | egrep 'chg$'
  * ./usr/bin/chg (glob)
chg should come with a man page
  $ dpkg --contents mercurial_*.deb | egrep 'man.*chg'
  * ./usr/share/man/man1/chg.1.gz (glob)