fix add-essential-files command

[syphar]

when working on making the local build work on my ARM, I stumbled on this issue where running cratesfyi build add-essential-files won't work any more.

This could be a regression from #1892 , though I don't fully understand why the change was made in that PR.

Any insight? @jsha @jyn514

[jyn514]

I suspect it was removed because it doesn't work for CI toolchains, only dist toolchains - @jsha can you confirm?

I think a better fix is to only run detect_toolchain_version for dist toolchains, instead of adding or removing it unconditionally.

[syphar]

I think a better fix is to only run detect_toolchain_version for dist toolchains, instead of adding or removing it unconditionally.

When I just used the result of detect_toolchain_version, and didn't set self.rustc_version, add_essential_files failed in a later step.

I'm happy to dig deeper when I know which way to go, @jsha do you have insight?

[jyn514]

I suspect it was removed because it doesn't work for CI toolchains, only dist toolchains - @jsha can you confirm?

Hmm, I added it back and it worked fine for CI toolchains. I think this is fine to merge as-is.

[jsha]

I'm a bit late commenting on this, but in https://github.com/rust-lang/docs.rs/pull/1892/files#diff-b06b44e6583254ce69af8cedabc04a73a97599d593676e1bbad7ee442240ccf1R204-R205 I mentioned that detect_rustc_version errors if run with a CI toolchain. It's interesting to hear from @jyn514 that that's changed; or maybe I was incorrect when I made that comment.

The reason I removed the call to detect_rustc_version from add_essential_files was indeed because it would error if called on a CI toolchain. I worked around that by setting it in update_toolchain instead. My analysis at the time was that add_essential_files was always and only called from update_toolchain, which would have made this refactoring correct. But I see now that was incorrect, and add_essential_files can be called directly from the command line. Thanks for caching and fixing.