…-gitea#31139)

This allows `nix flake metadata` and nix in general to lock a *branch*
tarball link in a manner that causes it to fetch the correct commit even
if the branch is updated with a newer version.

Co-authored-by: Jade Lovelace <[email protected]>
Co-authored-by: wxiaoguang <[email protected]>

…1139) (#31145)

Backport #31139 by @Mic92

This allows `nix flake metadata` and nix in general to lock a *branch*
tarball link in a manner that causes it to fetch the correct commit even
if the branch is updated with a newer version.

For further context, Nix flakes are a feature that, among other things,
allows for "inputs" that are "github:someuser/somerepo",
"https://some-tarball-service/some-tarball.tar.gz",
"sourcehut:~meow/nya" or similar. This feature allows our users to fetch
tarballs of git-based inputs to their builds rather than using git to
fetch them, saving significant download time.

There is presently no gitea or forgejo specific fetcher in Nix, and we
don't particularly wish to have one. Ideally (as a developer on a Nix
implementation myself) we could just use the generic tarball fetcher and
not add specific forgejo support, but to do so, we need additional
metadata to know which commit a given *branch* tarball represents, which
is the purpose of the Link header added here.

The result of this patch is that a Nix user can specify
`inputs.something.url =
"https://forgejo-host/some/project/archive/main.tar.gz"` in flake.nix
and get a link to some concrete tarball for the actual commit in the
lock file, then when they run `nix flake update` in the future, they
will get the latest commit in that branch.

Example of it working locally:

» nix flake metadata --refresh
'http://localhost:3000/api/v1/repos/jade/cats/archive/main.tar.gz?dir=configs/nix'
Resolved URL:
http://localhost:3000/api/v1/repos/jade/cats/archive/main.tar.gz?dir=configs/nix
Locked URL:
http://localhost:3000/api/v1/repos/jade/cats/archive/804ede182b6b66469b23ea4d21eece52766b7a06.tar.gz?dir=configs
/nix&narHash=sha256-yP7KkDVfuixZzs0fsqhSETXFC0y8m6nmPLw2GrAMxKQ%3D
Description:   Computers with the nixos
Path:          /nix/store/s856c6yqghyan4v0zy6jj19ksv0q22nx-source
Revision:      804ede182b6b66469b23ea4d21eece52766b7a06
Last modified: 2024-05-02 00:48:32

For details on the header value, see:

https://github.com/nixos/nix/blob/56763ff918eb308db23080e560ed2ea3e00c80a7/doc/manual/src/protocols/tarball-fetcher.md

Co-authored-by: Jörg Thalheim <[email protected]>
Co-authored-by: Jade Lovelace <[email protected]>
Co-authored-by: wxiaoguang <[email protected]>

* giteaofficial/main: (30 commits)
  Azure blob storage support (go-gitea#30995)
  Use repo as of renderctx's member rather than a repoPath on metas (go-gitea#29222)
  Ignore FindRecentlyPushedNewBranches err (go-gitea#31164)
  [skip ci] Updated translations via Crowdin
  Fix markup preview (go-gitea#31158)
  Swap word order in Comment and Close (go-gitea#31148)
  Fix push multiple branches error with tests (go-gitea#31151)
  Use vertical layout for multiple code expander buttons (go-gitea#31122)
  Remove duplicate `ProxyPreserveHost` in Apache httpd doc (go-gitea#31143)
  [skip ci] Updated translations via Crowdin
  Add an immutable tarball link to archive download headers for Nix (go-gitea#31139)
  Improve mobile review ui (go-gitea#31091)
  Add topics for repository API (go-gitea#31127)
  Add missed return after `ctx.ServerError` (go-gitea#31130)
  Fix API repository object format missed (go-gitea#31118)
  Fix DashboardRepoList margin (go-gitea#31121)
  Update JS dependencies (go-gitea#31120)
  [skip ci] Updated translations via Crowdin
  Prevent simultaneous editing of comments and issues (go-gitea#31053)
  Update demo site location from try.gitea.io -> demo.gitea.com (go-gitea#31054)
  ...