New file: gin-features.md

Describes features that have been added to GIN compared to upstream
GOGS.  In the future it might also point to specific parts
of the code where the changes are implemented.

This should be consulted when writing automated tests for GIN features
and reviewing the state of features when pulling in changes from
upstream.

Work in progress.

gin-features.md

@@ -0,0 +1,83 @@
+# GIN Features
+
+The following lists and describes the features added to the G-Node fork of GOGS, also known as *GIN Web*.
+
+## Git annex support
+
+The biggest and most important change is the support for large, binary file versioning using git-annex.  Git annex is supported both through git SSH uploads and downloads as well as the web interface.
+
+Git annex support via git-ssh is handled by the allowing clients to trigger `git-annex-shell` commands.
+
+Git annex support via the web is handled by:
+- replacing the `git add`, `git commit`, and `git push` commands in the upload backend with `git annex` equivalents, for upload.
+- peeking at the contents of files for the existence of a git-annex key and serving the annexed contents instead of the git file, for download.
+
+### Configuration options
+
+*WIP*
+
+- Annex size threshold
+
+### UI changes
+
+*WIP*
+
+- Missing annexed content
+
+## Unlisted public repositories
+
+In addition to having repositories be public or private, we also support having repositories be public but *unlisted*.
+This makes repositories accessible to all users that know the repository path (username/reponame) but does not list them in public places, like the Explore page and search results.
+
+### DB changes
+
+*WIP*
+
+- Unlisted column for repository.
+
+### UI changes
+
+*WIP*
+
+- Option in settings.
+
+## Invite via email
+
+Collaborators can be given access to a repository before they sign up to GIN.
+The owner of the repository can provide an email address on the Collaboration page of the repository settings.
+On submit, a user is created with the specified email address (using an autogenerated username) and an invitation link is sent to the address.
+The invitation link serves the same functionality as a password reset email, so the user is immediately asked to set a password when they follow the link.
+
+## DOI integration
+
+*WIP*
+
+### Configuration options
+
+*WIP*
+
+- DOI registration request address.
+- Shared key.
+
+### UI changes
+
+*WIP*
+
+- Repo page buttons.
+- Repo page badge.
+
+## Indexing and search integration
+
+*WIP*
+
+### Configuration changes
+
+*WIP*
+
+- GIN-Dex address
+
+### UI changes
+
+*WIP*
+
+- Search pages.