Patches since release of 0.7.0

Also add and use a flag to prevent autoupdates.

* Alire.Environment: sort env list for predictable output

* Alire.Environment: load env context from the platform

For the moment this is only used on Windows for msys2. Before this patch the msys2 env was not included in `alr print` which means that the context was not complete.

* Alr.Platforms.Windows: do not install msys2 if pacman already in PATH

This makes alr usable when the user is already in an msys2 context.
And it alse makes possible to have an alire package in msys2.

We use double-quote strings so single-quotes should not be escaped.

* Publish: report error causing unloadable manifest

* Testsuite: add test checking proper error output

* Avoid unneeded requests to update when no changes

Changes in solutions were being spuriously detected, in situations in which
there were no changes. Also, when manual changes didn't affect dependencies,
the situation was not corrected either by manual update or automatic check.

* New test to check the bugfix

To make this command more usable when converting an existing Ada project
to Alire, existing source or gpr files are now reported as a warning
instead of an error.

* policies.md: add best practices

* Update policies.md

* Update getting-started.md

* Update getting-started.md

* Typo

Otherwise it seems git defaults to the main branch, which manifested as
spurious "ahead" status, or ambiguous references in local remotes.

This could escape our checks when the alire.toml file was in .gitignore, for
example, so we didn't detect the discrepancy between local and remote sources.

This new version has a white layer for dark background desktop.

Fixes #582

It was using the old table notation.

This was already intended to work like this, but was buggy.

Update after #534

* Added paragraph about adding an ALR badge

* Incorporated review comments

* Clarified that the website is updated once daily
* Use 'crate' instead of 'project' where appropriate to avoid confusion
* Minor wording changes.

We were needlessly exploring the whole solution space, even when the best
complete solution had been already found.

It should not be used to specify default values.

* Update ci-linux.yml

Switch Linux CI to GitHub Ubuntu-18.04

* Update ci-linux.yml

* Update ci-linux.yml

Going back to GNAT community as GNAT-7 on Ubuntu-18.04 is not working.

Also remove obsolete env. var. BRANCH no longer needed as we no longer test the
old installer in this workflow.

* Getting started: spelling fixes

* README: add beta info and build instructions

* Use GitHub API for basic checks/info during publish

* Code review fix

* Fix: new config values unavailable during same run

New config entries were stored on disk but not added to the memory map. As the
Config.Set subprogram isn't aware of the level of configuration being set,
there is no direct way to both store to disk and to memory; instead the
solution is that the configuration is reloaded every time. This is a bit of
overkill and a candidate for later optimization.

* Alr.Platforms.Windows: download msys2 from GitHub releases

With the hope that GitHub servers are more reliable.

* Fix style

* Upload artifacts as assets to releases

* Remove obsolete workflow attempt

* Init: fill defaults with user-provided info

* Code review fixes

* Alire.Utils.User_Input: add function to query user's name, email and github login

* Break circular elaboration issue

Since Config uses Utils.User_Input indirectly via Deplyers.System, a
possibility is to move new User_Input functions that need Config into a new
package.

Co-authored-by: Alejandro R. Mosteo <amosteo@unizar.es>

* Alr.Commands: new Edit command

For the moment it opens GNATstudio within the Alire context.

* Alr.Commands.Init: add Create_Missing_Dirs

So the build won't fail if -p is not used with gprbuild.

* Fix test description

* testsuite/tests/workflows/edit: fix test when GNATstudio not in PATH

* Create tarball from alire workspace

* Tests for tarball creation

* Code review fixes

* Workaround for macOS BSD tar

* Document `alr publish --tar` changes.

* Fix tar regular expr and improve related test

It seems GNAT's Normalize_Arguments does its own escaping, so we do not need to
do it ourselves. Also, the test checks that indeed the `alire` folder is
excluded when tar'ing manually.