rust-tests: add test to check if `Cargo.lock` is up-to-date An out-of-date `Cargo.lock` is the source of rebase conflicts, prevents a reproductible build, introduces desync between the series that introduces a change in dependencies and the one that eventually commits the `Cargo.lock`, and is just a general annoyance. This commit demonstrates that the test works, the next one fixes the currently out-of-date `Cargo.lock`. Differential Revision: https://phab.mercurial-scm.org/D9079

scmutil: introduce function to check whether repo uses treemanifest or not In an upcoming patch, I wanted to check whether current repo uses treemanifest or not. I looked for a function and found that at all places we manually check for the requirement in repo requirements. I guess having a dedicated function for that is much better. Differential Revision: https://phab.mercurial-scm.org/D8981

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