chg: make is possible to call by default an hg binary located next to chg When a single version of hg is in use and it's in the PATH, using chg is just a matter of calling chg. But when there are multiple installations of hg+chg around, and hg is referred to with an absolute path, using chg is more annoying because it requires both changing the invocation to hg to use chg, but also setting CHGHG. Currently, we set HGPATH when we build chg to remove the need to set CHGHG in the previous paragraph. But that means chg now hardcodes its installation path, which makes the installation not relocatable. Hence this proposal to make chg find ./hg relative to itself (as opposed to CHGHG=./hg which find hg relative to cwd). This only works on linux as written, but since it's opt-in, it sounds fine. Tested by hand, as I'm not sure how else to test this. Differential Revision: https://phab.mercurial-scm.org/D9006

phases: fix performance regression with Python 2 Unlike Python 3, xrange doesn't support efficient "in" and uses a linear time scan instead. Expand the condition to handle it fast. Differential Revision: https://phab.mercurial-scm.org/D9072

rebase: move check for unresolved conflicts into lower-level rebasenode() I want to add another call to `rebasenode()` and it's better to not have to duplicate the check. Differential Revision: https://phab.mercurial-scm.org/D9075

rebase: add dryrun property to rebaseruntime I want to be able to check the property in `rebaseruntime._rebasenode()`. Passing the value via the runtime is a convenient way. Differential Revision: https://phab.mercurial-scm.org/D9074

rebase: when collapsing, p1 == dest, so use the former only `dest` is the destination we're rebasing onto, which is always the same as `p1` when using `--collapse`. This lets us simplify a bit. Differential Revision: https://phab.mercurial-scm.org/D9073

rebase: remove redundant isinmemory argument from _origrebase() The argument is redundant with `rbst.inmemory`, which makes it unclear what to do if they were somehow different. Differential Revision: https://phab.mercurial-scm.org/D9070

largefiles: prevent in-memory merge instead of switching to on-disk I enabled in-memory merge by default while testing some changes. I spent quite some time troubleshooting why largefiles was still creating an on-disk mergestate. Then I found out that it ignores the callers `wc` argument to `mergemod._update()` and always uses on-disk merge. This patch changes that so we raise an error if largefiles is used with in-memory merge. That way we'll notice if in-memory merge is used with largefiles instead of silently replacing ignoring the `overlayworkingctx` instance and updating the working copy instead. I felt a little bad that this would break things more for users with both largefiles and in-memory rebase enabled. So I also added a higher-level override to make sure that largefiles disables in-memory rebase. It turns out that that fixes `run-tests.py -k largefiles --extra-config-opt rebase.experimental.inmemory=1`. Differential Revision: https://phab.mercurial-scm.org/D9069

merge: add a back_out() function to encapsulate update() I've sent several earlier patches adding `merge.clean_update()`, `merge.merge()` etc, one function for each use case. This patch continues that work. I plan to hide the complex `update()` eventually. Differential Revision: https://phab.mercurial-scm.org/D9064

tests: update test-share-safe to work with non-zstd versions zstd is not available always like pure py versions. Hence we wrap that part around `#if zstd`. To make sure the functionality is tested on pure version as well, I have added another requirement addition test. Differential Revision: https://phab.mercurial-scm.org/D9045

rhg: add a limited `rhg cat -r` subcommand It only supports revision specification (rev or full hash) and the list of files to cat. Differential Revision: https://phab.mercurial-scm.org/D9052