Support downloading of symlinked tarballs

[jdemeyer]

#12426 introduces a new package "gfortran" which reuses the gcc tarball. This is done by symlinking various files in build/pkgs/gfortran to build/pkgs/gcc. This confuses the tarball downloader, so we add support for such symlinks in sage_bootstrap.

CC: @embray @vbraun @kiwifb

Component: build

Author: Jeroen Demeyer

Branch/Commit: 5b8e8dd

Reviewer: Dima Pasechnik

Issue created by migration from https://trac.sagemath.org/ticket/24476

[jdemeyer]

Branch: u/jdemeyer/support_downloading_of_symlinked_tarballs

[jdemeyer]

New commits:

5b8e8dd

Support downloading of symlinked tarballs

[jdemeyer]

Commit: 5b8e8dd

[vbraun]

comment:7

So whats the plan, have a symlinked tarball or two packages refer to the same tarball? The latter seems more sane to me. Whereas the former raises some questions, e.g. what to upload to mirrors.

Looking up tarball name -> package name isn't really important I think. Could just return a set of matching packages.

[kiwifb]

comment:8

Two packages referring to the same tarball. In #12426 I ended up creating a spkg for gfortran which of course uses gcc's tarball.

[jdemeyer]

comment:9

Replying to @vbraun:

Looking up tarball name -> package name isn't really important I think.

It is needed because the tarballs on the server are stored per package. The URL is something like .../spkg/upstream/gcc/gcc-7.2.0.xz, where gcc is the package name.

[dimpase]

comment:10

I am testing this together with #12426. If this is the only scenario to consider, this looks good. Should then #12426 become a dependence here?

[jdemeyer]

comment:11

Replying to @dimpase:

Should then #12426 become a dependence here?

No. Why should it be?

[dimpase]

comment:12

looks good to me.

[dimpase]

Reviewer: Dima Pasechnik

[vbraun]

Changed branch from u/jdemeyer/support_downloading_of_symlinked_tarballs to 5b8e8dd