opam 2.4 release

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We are extremely happy to announce the release of opam 2.4.0 and encourage all users to upgrade. Please read on for installation and upgrade instructions.

Major changes

• On opam init the compiler chosen for the default switch will no longer be ocaml-system (#3509) This was done because the system compiler (as-is your ocaml installed system wide, e.g. /usr/bin/ocaml) is known to be under-tested and prone to a variety of bugs and configuration issues. Removing it from the default compiler allows new-comers a more smooth experience. Note: if you wish to use it anyway, you are always able to do it explicitly using opam init --compiler=ocaml-system

• GNU patch and the diff command are no longer runtime dependencies. Instead the OCaml patch library is used (#6019, #6052, #3782, ocaml/setup-ocaml#933) Doing this we've removed some rarely used features of GNU Patch such as the support of Context diffs. The new implementation only supports Unified diffs including the git extended headers, however file permission changes via said extended headers have no effect.

• Add Nix support for external dependencies (depexts) by adding support for stateless package managers (#5982). Thanks to @RyanGibb for this contribution

• Fix opam install <local_dir> with and without options like --deps-only or --show-action having unexpected behaviours (#6248, #5567) such as:

  • reporting Nothing to do despite dependencies or package not being up-to-date
  • asking to install the wrong dependencies

UI changes

• opam show now displays the version number of packages flagged with avoid-version/deprecated gray (#6354)

• opam upgrade: Do not show the message about packages "not up-to-date" when the package is tagged with avoid-version/deprecated (#6271)

• Fail when trying to pin a package whose definition could not be found instead of forcing interactive edition (e.g. this could happen when making a typo in the package name of a pin-depends) (#6322)

New commands / options

• Add opam admin compare-versions to compare package versions for sanity checks. Thanks to @mbarbin for this contribution

• Add opam lock --keep-local to keep local pins url in pin-depends field (#4897)

• Add opam admin migrate-extrafiles which moves all extra-files of an existing opam repository into extra-sources. Thanks to @hannesm for this contribution

• The -i/--ignore-test-doc argument has been removed from opam admin check (#6335)

Other noteworthy changes

• opam pin/opam pin list now displays the current revision of a pinned repository in a new column. Thanks to @desumn for this contribution

• Symlinks in repositories are no longer supported (#5892)

• Fix sandboxing support in NixOS (#6333)

• Add the OPAMSOLVERTOLERANCE environment variable to allow users to fix solver timeouts for good (#3230)

• Fix a regression on opam upgrade <package> upgrading unrelated packages (#6373). Thanks to @AltGr for this contribution

• Fix pin-depends for with-* dependencies when creating a lock file (#5428)

• opam admin check now sets with-test and with-doc to false instead of true

• Add apt-rpm/ALTLinux family support for depexts. Thanks to @RiderALT for this contribution

• Fix the detection of installed external packages on OpenBSD to not just consider manually installed packages (#6362). Thanks to @semarie for this contribution

• Disable the detection of available system packages on SUSE-based distributions (#6426)

ystem,dune,beginner,dev,new project

Changes

• opam switch create [name] <version> will not include compiler packages flagged with avoid-version/deprecated in the generated invariant anymore (#6494). This will allow opam to avoid the use of the ocaml-system package unless actually explicitly requested by the user. The opam experience when the ocaml-system compiler is used is known to be prone to a variety of bugs and configuration issues.
• Cygwin: Fallback to the existing setup-x86_64.exe if its upgrade failed to be fetched (#6495, partial fix for #6474)
• Fix a memory leak happening when running large numbers of commands or opening large number of opam files (#6484). Thanks to @hannesm for this contribution
• Remove handling of the OPAMSTATS environment variable (#6485). Thanks to @hannesm for this contribution

Changes

• Fixed some bugs in opam install --deps-only (and other commands simulating package pins, such as --depext-only) more visible in 2.4:
  • When a package pkg is already installed and opam install ./pkg --deps is called, if there is a conflict between the installed pkg dependencies and the definition of the local pkg, the conflict was not seen and the already installed pkg was kept (#6529)
  • No longer fetch and write the sources when simulating packages that were already pinned (#6532)
  • opam was triggering the reinstall of the package based on the already pinned packages instead of the expected newly simulated pinned packages (#6501)
  • opam was using the opam description of the wrong package in some cases (#6535)
• Change the behaviour of --deps-only, where it no longer requires unicity of package version between the request and the installed packages. In other words, if you have pkg.1 installed, installing dependencies of pkg.2 no longer removes pkg.1. This also allows to install dependencies of conflicting packages when their dependencies are compliant. (#6520)

Windows binary

• Improve the prebuilt Windows binaries by including Cygwin's setup-x86_64.exe in the binary itself as fallback, in case cygwin.com is inaccessible (#6538)

NOTE: this article is cross-posted on opam.ocaml.org and ocamlpro.com.

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