RFR: 1431: The method TestPullRequest#diff sometimes returns wrong information

[Magnus Ihse Bursie]

On Sat, 20 Aug 2022 07:53:23 GMT, Guoxiong Li <gli at openjdk.org> wrote:

> Hi all,
> 
> The method `TestPullRequest#diff` always passes the head hash of the target branch to the method `Repository#diff` as the base hash. But it may be wrong when the target branch was submitted some new commits after creating the pull request. `TestPullRequest#diff` should find the last common hash of the source and target branch as the base hash.
> 
> This patch fixes the bug and adds the test case. I don't know whether it is good to place the test case at the class `CSRBotTests`, but the method `CSRBotTests#testBackportCsr` indeed contains the situation of this bug.
> 
> Thanks for taking the time to review.
> 
> Best Regards,
> -- Guoxiong

test/src/main/java/org/openjdk/skara/test/TestPullRequest.java line 257:

> 255:             var baseHash = sourceHash;
> 256:             var targetBranch = new Branch(targetRef());
> 257:             while (!"0".repeat(40).equals(baseHash.hex())) {

So if the common commit is more than 40 commits away, return "no diff"? :-)

This is only used in testing, right? If so, this you could get away with it, but I think a comment describing the limitations would be needed.

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PR: https://git.openjdk.org/skara/pull/1360