lfs: show a friendly message when pushing lfs to a server without lfs enabled Upfront disclaimer: I don't know anything about the wire protocol, and this was pretty much cargo-culted from largefiles, and then clonebundles, since it seems more modern. I was surprised that exchange.push() will ensure all of the proper requirements when exchanging between two local repos, but doesn't care when one is remote. All this new capability marker does is inform the client that the extension is enabled remotely. It may or may not contain commits with external blobs. Open issues: - largefiles uses 'largefiles=serve' for its capability. Someday I hope to be able to push lfs blobs to an `hg serve` instance. That will probably require a distinct capability. Should it change to '=serve' then? Or just add an 'lfs-serve' capability then? - The flip side of this is more complicated. It looks like largefiles adds an 'lheads' command for the client to signal to the server that the extension is loaded. That is then converted to 'heads' and sent through the normal wire protocol plumbing. A client using the 'heads' command directly is kicked out with a message indicating that the largefiles extension must be loaded. We could do similar with 'lfsheads', but then a repo with both largefiles and lfs blobs can't be pushed over the wire. Hopefully somebody with more wire protocol experience can think of something else. I see 'x-hgarg-1' on some commands in the tests, but not on heads, and didn't dig any further.

lfs: allow non-lfs exchanges when the extension is only enabled on one side Once the 'lfs' requirement is added, the extension must be loaded on both sides, and changegroup3 used. But there's no reason that I can see for bailing with cryptic errors if lfs is not required, but randomly enabled somewhere.

lfs: add the 'lfs' requirement in the changegroup transaction introducing lfs A hook like this is how largefiles manages to do the same. Largefiles uses a changegroup hook, but this uses pretxnchangegroup because that actually causes the transaction to rollback in the unlikely event that writing the requirements out fails. Sadly, the requires file itself isn't rolled back if a subsequent hook fails, but that seems trivial. Now that commit, changegroup and convert are covered, I don't think there's any way to get an lfs repo without the requirement. The grep exit code is blotted out of some test-lfs-serve.t tests now showing the requirement, because run-tests.py doesn't support conditionalizing the exit code.

test-lfs: add tests covering http exchanges This tries to test every combination of having the extension enabled/disabled on each side, and then push/pull/clone/identify lfs and non-lfs content. SSH is ignored here, because there's enough going on as it is. The root issue here is again that requirements are not exchanged and preserved on push/pull/clone. Doing so should eliminate the cryptic error messages when using `hg serve`. The 500 server error is triggered by "ValueError: no common changegroup version", because the extension forces changegroup3. Or, if changegroup3 is enabled manually, it is triggered by "abort: missing processor for flag '0x2000'!". Sadly, run-tests.py doesn't support conditionalizing the exit code like it does lines of output. Therefore, a couple of tests blot out the exit code by appending "|| true", since these failures will go away shortly anyway.

test-lfs: add tests covering local exchanges The root issue here is that requirements are not exchanged and preserved on push/pull. This can be handled with a changegroup hook. Testing for remote exchanges is much more extensive (it's possible for one process or the other to not have the extension loaded at all), so it is added separately.

smartset: split generatorset classes to avoid cycle I uncovered a cycle manifesting in a memory leak by running `hgperfrevset '::tip'`. The cycle was due to generatorset.__init__ assigning a bound method to self.__contains__. Internet sleuthing revealed that assigning a bound method to an instance attribute always creates a cycle. This commit creates two new variants of generatorset for the special cases of ascending and descending generators. The special implementations of __contains__ have been extracted to these classes where they are defined as __contains__. generatorset now implements __new__ and changes the spawned type to one of the new classes if needed. Differential Revision: https://phab.mercurial-scm.org/D1780

merge: raise before running mergedriver if using IMM Merge driver scripts run in the working copy, so disable with IMM for now. Differential Revision: https://phab.mercurial-scm.org/D1781

scmutil: use a tuple of possible values instead of using startswith() This patch also adds a review comment which is helpful as inline comment. Differential Revision: https://phab.mercurial-scm.org/D1761

show: use revlog function to compute length of the longest shortest node As the core part of shortest() was extracted at 448725a2ef73, we no logner need a templater.

commands: use the new API to access hidden changesets in various commands In previous patches, we have added an internal API to unhide hidden changesets. This patch makes the following command use that api in nowarn mode i.e. there will be no warning while accessing hidden changesets. cat, diff, export, files, heads, identify, log, manifest, parents, status This patch also adds test demonstarting the behaviour. .. feature:: Accessing hidden changesets Set config option 'experimental.directaccess = True' to access hidden changesets from read only commands. Differential Revision: https://phab.mercurial-scm.org/D1735