Description
Is your feature request related to a problem? Please describe.
It's often useful to build or run something from a PR, especially when reviewing.
Let's make this easier.
Describe the solution you'd like
Step 1: CLI only
GitHub already supports a magic ref, like github:NixOS/nix?ref=refs/pull/11159/merge
We could provide a shorthand for this, like github:NixOS/nix?merge=11159
These merge commits, as well as commits in the PR tend to disappear, so it's doesn't make sense to lock this by rev sha.
Print a little notice when the PR has been merged, to let the user remove the merge parameter.
Step 2: Locking
Store the diff in the lock file or a location relative to it.
This would make it viable for use in pure-eval mode and real locking.
Step 3: Multiple
Multiple PRs could be merged in a single fetching. GitHub doesn't do this for us, so this would need the logic of Step 2, which needs to implement its own patching anyway.
Describe alternatives you've considered
Additional context
- Lazy trees #6530 also implements patching functionality
Priorities
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