Today I Learned: Overlapping pull requests in Pagure

April 3, 2016
Tagged as: TIL, Fedora, Pagure.

The other day I was wondering what happens when two pull requests in Pagure share some commits. So I tested it out and here are the results.

By sharing commits I mean one pull request is based on another. (In the spirit of git log, newest commits on the top.)

 * d69de04 (pr2) Extra commit
 * 9657821 (pr1) Shared commit
*  4ec8ad5 (master) Last commit on master

Assuming both pull requests are to be merged, there are two ways to approach this.

  1. Merge pr1 first. The merge happens as usual, and pr2 will get a notification comment saying it was rebased. Merging pr2 now can still use fast-forward strategy.

  2. Merge pr2 first. Again, there is no problem merging, and in this situation Pagure will say that there are no changes on pr1 to be merged, so you can just close this pull request and be done with it.

Now I don't know if it was designed like this or its just an outcome of the ways things are implemented, but it seems to behave logically. As far as I know this is not documented, so I would not be surprised to see changes.

What happens when one pull request is not just a subset of another, but is a diverging history? In the example, think pr1 has also an extra commit not shared with pr2.

No matter which request is merged first, the other will be automatically rebased so that it is only requesting to merge the extra commits. It may or may not create a merge conflict. This really depends on the nature of the actual changes.