Check if directory is free to be used

[AdaOrbit]

This PR solves #2066 by checking if the chosen project name is free.
for --in-place it looks if alire.toml already exists. On normal project creation it checks for <project name>/alire.toml

PR creation checklist

• A test is included, if required by the changes.
• doc/user-changes.md has been updated, if there are user-visible changes.
• doc/catalog-format-spec.md has been updated, if applicable.
• BREAKING.md has been updated for major changes in alr, minor/major in catalog format.

[AdaOrbit]

@AldanTanneo @mosteo ready for review!

[AldanTanneo]

Ideally, there would be an error (overridable with --force) if the target directory is not empty (we don't want to overwrite existing files, or fail with a partially initialized crate.)

Is this done already elsewhere?

[AdaOrbit]

The current behavior is to partially initialize a crate if alire.toml already exists. Runnig alr init --no-skel foo and then alr init foo results in foo.gpr, share/ and src/foo.ads being created but then erroring out because alire.toml exists and skipping alire/ creation.

And if I understand it correctly alire.toml is what makes a directory an alire crate. What I do to mitigate this is by checking if the alire.toml file already exists. Thus stopping the user from partial creation.

I tried finding something similar that does those checks in the code base but couldn't find anything. (Maybe you know more and could guide me?)

Also a comment on the --force command for init: I don't think that it is a good idea. It should rather be the developers responsibility on ensure all the files that alire is going to "overwrite" are already gone and usable. Or else we end up with users who ask "I used --force and main.gpr, src/main.ads and more got overwriten. How to fix?"

[AldanTanneo]

Also a comment on the --force command for init: I don't think that it is a good idea. It should rather be the developers responsibility on ensure all the files that alire is going to "overwrite" are already gone and usable. Or else we end up with users who ask "I used --force and main.gpr, src/main.ads and more got overwriten. How to fix?"

What I meant is not using --force to overwrite files, but to say "try anyway" when the directory is not empty. It would still fail if it tries to overwrite existing user files.

Detecting when the directory is not empty would avoid the partial crate initialization altogether, and then using --force would potentially end up with a partially initialized crate (with skeleton files) but the error would not be alr's fault. Does that make sense?

[AldanTanneo]

Of course, this can be on top of alire.toml detection, as the crate creation would fail unconditionally if there is already an alire.toml file present.

[AdaOrbit]

I should look more into the control flow to understand the current design better. I'll take a look at it again and see where it's best to check and add features.