archive: support dot-slash-prefixed paths for Tar-formats

[tgolsson]

Is your feature request related to a problem? Please describe.

Some tools (e.g. the Deploy Pages GH Action) prefer and/or require paths that are explicitly relative, with a leading ./ on every path. Pants currently generates archives without this prefix. While not overly complex to manually fix it after packaging, it might be useful to allow this as an option.

Describe the solution you'd like

The ability to specify a path_prefix for tar-like formats.

Describe alternatives you've considered

Manually fixing it seems the most consistent. I was not able to get the right results with relocated_files.

Additional context

• See above issue link for a clear issue caused by the current format.
• I can contribute the changes necessary here if this seems like a good change.

[AlexTereshenkov]

Hey @tgolsson! I am very sorry, I don't follow what kind of prefix you refer to? A file cannot contain /, so I am puzzled by

Pants currently generates archives without this prefix.

I must be missing something, apologies.

[tgolsson]

Let's imagine this directory:

a-directory/
└── file.foobar
foo.txt
bar.txt

fed into a tar command. I can pass them in two different ways:

tar xf out.tar a-directory/file.foobar foo.txt bar.txt
tar xf out.tar ./a-directory/file.foobar ./foo.txt ./bar.txt

Because tar maintains the full path, those ./ they lead to a slightly different layout in the final archive. Apparently some tools use the ./ for validation, and so it'd be nice if Pants could generate archives on this format as well.

You can find more examples here or here

[AlexTereshenkov]

Gotcha, now it makes sense to me.

I wonder if there are any other kind of prefixes that one would find useful to apply? As it seems to be a common requirement and there is awareness about this layout, perhaps we shall differentiate between producing a tar with dot-slash and without? So instead of an arbitrary prefix, have a boolean instead (--secure-dot-slash or something like this). But if there are other legit cases for having a variety of prefixes, then perhaps a prefix would be a better option.

[tgolsson]

I went back and forth on it. I do think that just supporting dot-slash is easier and clearer, as any other prefixing can be achieved with relocated_files.

[AlexTereshenkov]

Right, so perhaps a new field on the archive target?

[tgolsson]

Yeah. Something like force_relative_paths: bool maybe?