Currently we rely on different sources to present merge request diffs, these include:
Currently we rely on different sources to present diffs, these include:
- Rugged gem
- Gitaly service
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@@ -11,6 +11,8 @@ We're constantly moving Rugged calls to Gitaly and the progress can be followed
## Architecture overview
### Merge request diffs
When refreshing a Merge Request (pushing to a source branch, force-pushing to target branch, or if the target branch now contains any commits from the MR)
we fetch the comparison information using `Gitlab::Git::Compare`, which fetches `base` and `head` data using Gitaly and diff between them through
`Gitlab::Git::Diff.between` (which uses _Gitaly_ if it's enabled, otherwise _Rugged_).
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@@ -32,6 +34,17 @@ In order to present diffs information on the Merge Request diffs page, we:
3. If the diff file is cacheable (text-based), it's cached on Redis
using `Gitlab::Diff::FileCollection::MergeRequestDiff`
### Note diffs
When commenting on a diff (any comparison), we persist a truncated diff version
on `NoteDiffFile` (which is associated with the actual `DiffNote`). So instead
of hitting the repository every time we need the diff of the file, we:
1. Check whether we have the `NoteDiffFile#diff` persisted and use it
2. Otherwise, if it's a current MR revision, use the persisted
`MergeRequestDiffFile#diff`
3. In the last scenario, go the the repository and fetch the diff
## Diff limits
As explained above, we limit single diff files and the size of the whole diff. There are scenarios where we collapse the diff file,
