rust-chg: add helper to pack environment variables On my machine, "printenv | wc -c" says 3422. That's the only reason why the initial buffer capacity is set to 4kB. Differential Revision: https://phab.mercurial-scm.org/D8363

rust-chg: move set_current_dir() to Locator This is necessary to run config validation in proper environment. Differential Revision: https://phab.mercurial-scm.org/D8362

rust-chg: abort if server doesn't have required capabilities It's checked at Locator::connect() since we'll have to do more stuff in this function. Differential Revision: https://phab.mercurial-scm.org/D8361

rust-chg: spawn server process if not running This is the minimal reimplementation of gethgcmd(), execcmdserver(), retryconnectcmdserver(), and connectcmdserver() in chg.c. No config validation is implemented yet. And some Py3 workarounds would be missing as this is the code I wrote in 2018. Differential Revision: https://phab.mercurial-scm.org/D8360

rust-chg: update dependencies Differential Revision: https://phab.mercurial-scm.org/D8359

rust-chg: depend on released version of tokio-process Still it is futures-0.1 based. Differential Revision: https://phab.mercurial-scm.org/D8358

rust-chg: add brief comment about initial capacity of temp_sock_path() I don't know if it can be expressed as a compile-time constant, so it's a comment for now. About this series: This is quite old patches for rust-chg. I heard from Octobus people that there's a plan to do an experiment on merging hgcli + chg + some Rust?, so I decided to respin the rust-chg series. Maybe we'll rewrite the core to leverage the recent async/await functionality, but I want to first make my old patches in so the rust-chg can be a drop-in replacement for the chg of C. Compiler warnings will be removed later, and the codebase will be upgraded to the 2018 edition later. Differential Revision: https://phab.mercurial-scm.org/D8357

discovery: avoid wrongly saying there are nothing to pull We can get in a situation where a revision passed through `hg pull --rev REV` are available on the server, but not a descendant of the advertised server heads. For example the server could lying be during heads advertisement, to hide some pull request. Or obsolete/hidden content could be explicitly pulled. So in this case the lookup associated to `REV` returned successfully, but the normal discovery will find all advertised heads already known locally. This flip a special boolean `anyinc` that will prevent any fetch attempt, preventing `REV` to be pulled over. We add three line of code to detect this case and make sure a pull actually happens. My main target is to make some third party extensions happy (I expect the associated test to move upstream with the extension). However this fix already make some of the `infinitepush` test happier.

rebase: don't create merge when continuing rebase interrupted by old hg This fixes the bug described and demonstrated in the previous commit. It does so by practically undoing 8082a77cc3a2 (rebase: remove some redundant setting of dirstate parents, 2020-01-10). Differential Revision: https://phab.mercurial-scm.org/D8356

tests: demonstrate how continuing rebase after upgrade can result in merge If the user starts a rebase with an hg version before 9c9cfecd4600 (rebase: don't use rebased node as dirstate p2 (BC), 2020-01-10) and then runs into conflicts, they will be dropped out to the shell with the rebased node set as the dirstate's second parent. If they then upgrade to a later hg version, it will respect the dirstate's parents and will create a merge commit even if the user was rebasing a non-merge commit. Differential Revision: https://phab.mercurial-scm.org/D8355