This replaces --_skip-to-install and is suitable for people who have audited letsencrypt-auto and wish to run it as is, without upgrading to the latest version.
Also...
* rm temp dirs when done. No longer reuse a single temp dir across phases so the user doesn't have to pass a temp dir with --no-self-upgrade as phase 1 itself used to.
* Swap stanzas in the big "if" so we aren't testing negatives all the time.
* Fix a bug in which we ran peep with $LE_PYTHON rather than the python in the venv.
* Bootstrap only if it looks like we never got to the point of making a venv before.
* Move venv creation into Phase 2. Besides the practical benefit of ensuring there's a venv if a user passes --no-self-upgrade, this has the philosophical advantage of making Phase 1 more minimal, giving us more latitude to change behavior in updates.
Change template language to reference files, saving me some boilerplate over the dict-based .format() thing I originally had in mind.
Put newlines at the ends of bootstrap scripts. It makes the built le-auto script prettier.
They're now used only by the le-auto build process. The new public interface for OS-level bootstrapping is le-auto --os-packages-only, which dispatches by OS automatically. That obsoletes install-deps.sh as well, saving some repetition.
Also, switch to mustache-style templating to avoid colliding with shell variable references.
To optimize for the docker cache, we could later add a shim script that sources just deb_common.sh and calls its bootstrap function.
This makes the script more readable and easier to work on. We'll stitch it together with a build process.
Also, stop passing the sudo command as an arg to the experimental bootstrappers. They will be inlined into the main script and can just reference $SUDO. As a result, stop recommending devs run the scripts manually, instead running le-auto --os-packages-only. This has the nice side effect of making dev documentation simpler.
Name the folder "letsencrypt_auto" rather than "letsencrypt-auto" because git yield endless pain when replacing a file with a dir. Perhaps we can change it with impunity in a latter commit.
Erik Rose