py3: add 9 new passing tests caught by buildbot Differential Revision: https://phab.mercurial-scm.org/D5284

branch: allow changing branch of merge commits with --rev Tests show that changing branch of merge commits works fine with evolution and without, so let's allow it. Other safeguards should prevent users from shooting themselves in the foot.

lfs: ensure that the return of urlopener.open() is closed No problem observed, just an oversight noticed while reading documentation.

changegroup: avoid instantiating storage if we are not using it Differential Revision: https://phab.mercurial-scm.org/D5280

http: allow 'auth.prefix' to have a username consistent with the URI It may be a little weird to put a username in the prefix, but the documentation doesn't disallow it, and silently disallowing it has caused confusion[1]. The username must match what is passed in (which seems to be from the URI via a circuitous route), as well as 'auth.username' if it was specified. I thought about printing a warning for a mismatch, but we already don't print a warning if the 'auth.username' and URI username don't match. This change allows the first and second last new test cases to work as expected. It looks like this would have been a problem since at least 0593e8f81c71. [1] https://www.mercurial-scm.org/pipermail/mercurial/2018-November/051069.html

lfs: make the exception messages consistent I don't love that it repeats 'HTTP Error' in an already long message, but I doubt that we should assume that it will always say that on the original exception message.

lfs: handle URLErrors to add additional information Sometimes the blob server is hit first (e.g. on push), and sometimes it's hit last (e.g. pull). Throw in depth first subrepo operations, and things quickly get insane. It wasn't even mentioning LFS, so just saying "connection refused" can be confusing- especially if the blob server is a secondary server and connecting to the repo server works. The exception handler for the transfer handler will print the full path to the blob, but that seems fine given that it might be necessary to debug a second server. (We don't yet support a standalone blob server, so the handler for the Batch API will cover 99.9% of the current problems. But it might as well be handled now while I'm thinking about it.) The function for translating to a message was mostly borrowed from scmutil.catchall().

lfs: improve the hints for common errors in the Batch API The previous message was too debug-ish and less action oriented than a hint should be. The remaining errors that aren't handled are more along the lines of programming errors (not using POST, bad accept type, etc), so I'm not bothering with that. The friendly errors purposely use `self.baseurl` instead of the full Batch API endpoint because I'd expect some copy/paste/modify on the part of the user here, and it would be more confusing if '/objects/batch' magically appeared, but shouldn't be used in the config setting. It still seems like the right thing for debugging in the catchall case.

lfs: provide more Batch API error info via a hint in the raised exception A coworker had a typo in `lfs.url`, forgot it was even set because usually the blob server is inferred, and then got a 404. It would have been easier to debug with the failing URL printed.

scmutil: display the optional hint when handling StorageError in catchall() Other than CensoredNodeError (which is also a StorageError), it looks like all exceptions with a hint display them. I'm not sure that it makes sense to have a hint for censored nodes, so I'm not bothering with that. It looks like nobody is using this yet, as the tests don't change.