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Improve initial arc land experience when destination repo is empty
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Description

When a user clones an empty Diffusion repository, attempting to arc land the initial commit results in this mostly-unhelpful error:

[2017-06-27 19:10:22] EXCEPTION: (Exception) Branch "master" does not exist in remote "origin". at [<arcanist>/src/land/ArcanistGitLandEngine.php:101]

This requires the user to manually do a git push to get the ball rolling. It would be nice if arc land would detect that the repository is empty and offer to initialize it for the user, by pushing the current branch.

Event Timeline

avivey added a subscriber: avivey.Jun 29 2017, 4:26 AM

in T6722#197239 I had the same problem with "land revision from Web UI" :)

epriestley moved this task from Backlog to arc land on the Arcanist board.Oct 25 2019, 6:02 PM

I think the general shape of this is:

  • Use git hash-object to build an empty commit pointing at the empty tree.
  • Squash or merge onto it.

This gives us a commit with the correct tree, and allows us to execute all the normal squash/merge code (we have a legitimate "into" target).

Then:

  • If we squashed, use git hash-object to write a new commit which is identical to the result, but has no parent.
  • If we merged, use git hash-object to write a new commit which is identical to the merge commit, but has only one parent.

Finally, use the commit which came out of that step as the final outcome of the process.

This means we end up with a small amount of unique code which only runs occasionally during this workflow, but most of the code can be shared: we don't have to write completely unique "if empty" merge strategies.

epriestley triaged this task as Wishlist priority.
epriestley removed a project: Feature Request.