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Start archive downloads immediately #44

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@matrss matrss commented Oct 30, 2023

This is a follow up to #43.

Right now, gitea waits until an archive is generated before the download of that archive starts. For small repositories this is fine, but for larger repositories this can mean a rather long wait time until anything happens at all.

This PR changes the download logic to immediately "stream" the archive, that is still being generated, to the user who requested the archive. This is done by creating a (additional) temporary copy of the archive while it is being created. This temporary copy is then read from and served to the user until this temporary file is deleted, i.e. the archive generation is finished. If there are additional requests to download the same archive while it is still being generated then the same temporary file is reused.

After the archive generation finished any further requests to get the archive are handled just like they were without this change.

This approach has a few downsides:

  1. Since the archive size is not known in advance the downloading program (e.g. the browser) can not display a meaningful progress bar.
  2. It does not reuse the temporary file that the LocalStorage backend already creates for the archive, therefore doubling the required disk space while the archival process is running.

Still WIP.

kousu and others added 8 commits October 30, 2023 13:11
[git-annex](https://git-annex.branchable.com/) is a more complicated cousin to
git-lfs, storing large files in an optional-download side content.  Unlike lfs,
it allows mixing and matching storage remotes, so the content remote(s) doesn't
need to be on the same server as the git remote, making it feasible to scatter
a collection across cloud storage, old harddrives, or anywhere else storage can
be scavenged.  Since this can get complicated, fast, it has a content-tracking
database (`git annex whereis`) to help find everything later.

The use-case we imagine for including it in Gitea is just the simple case, where
we're primarily emulating git-lfs: each repo has its large content at the same URL.

Our motivation is so we can self-host https://www.datalad.org/ datasets, which
currently are only hostable by fragilely scrounging together cloud storage --
and having to manage all the credentials associated with all the pieces -- or at
https://openneuro.org which is fragile in its own ways.

Supporting git-annex also allows multiple Gitea instance to be annex remotes for
each other, mirroring the content or otherwise collaborating the split up the
hosting costs.

Enabling
--------

TODO

HTTP
----

TODO

Permission Checking
-------------------

This tweaks the API in routers/private/serv.go to expose the calling user's
computed permission, instead of just returning HTTP 403.

This doesn't fit in super well. It's the opposite from how the git-lfs support is
done, where there's a complete list of possible subcommands and their matching
permission levels, and then the API compares the requested with the actual level
and returns HTTP 403 if the check fails.

But it's necessary. The main git-annex verbs, 'git-annex-shell configlist' and
'git-annex-shell p2pstdio' are both either read-only or read-write operations,
depending on the state on disk on either end of the connection and what the user
asked it to ask for, with no way to know before git-annex examines the situation.
So tell the level via GIT_ANNEX_READONLY and trust it to handle itself.

In the older Gogs version, the permission was directly read in cmd/serv.go:

```
mode, err = db.UserAccessMode(user.ID, repo)
```
- https://github.com/G-Node/gogs/blob/966e925cf320beff768b192276774d9265706df5/internal/cmd/serv.go#L334

but in Gitea permission enforcement has been centralized in the API layer.
(perhaps so the cmd layer can avoid making direct DB connections?)

Deletion
--------

git-annex has this "lockdown" feature where it tries
really quite very hard to prevent you deleting its
data, to the point that even an rm -rf won't do it:
each file in annex/objects/ is nested inside a
folder with read-only permissions.

The recommended workaround is to run chmod -R +w when
you're sure you actually want to delete a repo. See
https://git-annex.branchable.com/internals/lockdown

So we edit util.RemoveAll() to do just that, so now
it's `chmod -R +w && rm -rf` instead of just `rm -rf`.
Fixes neuropoly#11

Tests:

* `git annex init`
* `git annex copy --from origin`
* `git annex copy --to origin`

over:

* ssh

for:

* the owner
* a collaborator
* a read-only collaborator
* a stranger

in a

* public repo
* private repo

And then confirms:

* Deletion of the remote repo (to ensure lockdown isn't messing with us: https://git-annex.branchable.com/internals/lockdown/#comment-0cc5225dc5abe8eddeb843bfd2fdc382)

------

To support all this:

* Add util.FileCmp()
* Patch withKeyFile() so it can be nested in other copies of itself

-------

Many thanks to Mathieu for giving style tips and catching several bugs,
including a subtle one in util.filecmp() which neutered it.

Co-authored-by: Mathieu Guay-Paquet <[email protected]>
This makes HTTP symmetric with SSH clone URLs.

This gives us the fancy feature of _anonymous_ downloads,
so people can access datasets without having to set up an
account or manage ssh keys.

Previously, to access "open access" data shared this way,
users would need to:

  1. Create an account on gitea.example.com
  2. Create ssh keys
  3. Upload ssh keys (and make sure to find and upload the correct file)
  4. `git clone [email protected]:user/dataset.git`
  5. `cd dataset`
  6. `git annex get`

This cuts that down to just the last three steps:

  1. `git clone https://gitea.example.com/user/dataset.git`
  2. `cd dataset`
  3. `git annex get`

This is significantly simpler for downstream users, especially for those
unfamiliar with the command line.

Unfortunately there's no uploading. While git-annex supports uploading
over HTTP to S3 and some other special remotes, it seems to fail on a
_plain_ HTTP remote. See neuropoly#7
and https://git-annex.branchable.com/forum/HTTP_uploads/#comment-ce28adc128fdefe4c4c49628174d9b92.

This is not a major loss since no one wants uploading to be anonymous anyway.

To support private repos, I had to hunt down and patch a secret extra security
corner that Gitea only applies to HTTP for some reason (services/auth/basic.go).

This was guided by https://git-annex.branchable.com/tips/setup_a_public_repository_on_a_web_site/

Fixes neuropoly#3

Co-authored-by: Mathieu Guay-Paquet <[email protected]>
This moves the `annexObjectPath()` helper out of the tests and into a
dedicated sub-package as `annex.ContentLocation()`, and expands it with
`.Pointer()` (which validates using `git annex examinekey`),
`.IsAnnexed()` and `.Content()` to make it a more useful module.

The tests retain their own wrapper version of `ContentLocation()`
because I tried to follow close to the API modules/lfs uses, which in
terms of abstract `git.Blob` and `git.TreeEntry` objects, not in terms
of `repoPath string`s which are more convenient for the tests.
Previously, Gitea's LFS support allowed direct-downloads of LFS content,
via http://$HOSTNAME:$PORT/$USER/$REPO/media/branch/$BRANCH/$FILE
Expand that grace to git-annex too. Now /media should provide the
relevant *content* from the .git/annex/objects/ folder.

This adds tests too. And expands the tests to try symlink-based annexing,
since /media implicitly supports both that and pointer-file-based annexing.
This updates the repo index/file view endpoints so annex files match the way
LFS files are rendered, making annexed files accessible via the web instead of
being black boxes only accessible by git clone.

This mostly just duplicates the existing LFS logic. It doesn't try to combine itself
with the existing logic, to make merging with upstream easier. If upstream ever
decides to accept, I would like to try to merge the redundant logic.

The one bit that doesn't directly copy LFS is my choice to hide annex-symlinks.
LFS files are always _pointer files_ and therefore always render with the "file"
icon and no special label, but annex files come in two flavours: symlinks or
pointer files. I've conflated both kinds to try to give a consistent experience.

The tests in here ensure the correct download link (/media, from the last PR)
renders in both the toolbar and, if a binary file (like most annexed files will be),
in the main pane, but it also adds quite a bit of code to make sure text files
that happen to be annexed are dug out and rendered inline like LFS files are.
Upstream can handle the full test suite; to avoid tedious waiting,
we only test the code added in this fork.
matrss and others added 4 commits October 31, 2023 13:37
This extends the archive creation logic to add annexed files to the
created archives. The basic flow is this:
1. Create an archive using `git archive`
2. Read in that archive and write out a new one, replacing all annexed
   files with their annexed content; leaving the git-only files as-is

The file permissions with which the annexed files are put into the
archive are decided based on what `git archive` does for other files as
well:
- For tar.gz archives, executable files get permissions 0775 and regular
  files get 0664.
- For zip archives, executable files get permissions 0755 and regular
  files are archived with "FAT permissions" rw, instead of unix
  permissions.

If for a given archive request an annexed file is not present on the
gitea instance then the content as tracked by git (i.e. a symlink or
pointer file) is silently put into the resulting archive instead.

Co-authored-by: Nick Guenther <[email protected]>
Tests include:
- Compare the list of files in the resulting archive with the list of
  files as tracked in the archived git tree.
- Compare the content of each file with what it should be (git blob
  content or the annexed file, respectively).
- Check that the file mode matches the expected file mode for all
  archived files.
- Check that the resulting archive has the archived commitID set as a
  comment (as `git archive` does as well).

The tests are done for both the "web" endpoints at
`/<user>/<repo>/archive/<git-ref>.{tar.gz,zip}` and the "api-v1"
endpoints at `/api/v1/<user>/<repo>/archive/<git-ref>.{tar.gz,zip}`.
This commit can be dropped as soon as
go-gitea#27563 is accepted.
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