OPAM 1.2.1 has just been released. This patch version brings a number of fixes and improvements over 1.2.0, without breaking compatibility.

Upgrade from 1.2.0 (or earlier)

See the normal installation instructions: you should generally pick up the packages from the same origin as you did for the last version -- possibly switching from the official repository packages to the ones we provide for your distribution, in case the former are lagging behind.

What's new

No huge new features in this point release -- which means you can roll back to 1.2.0 in case of problems -- but lots going on under the hood, and quite a few visible changes nonetheless:

• The engine that processes package builds and other commands in parallel has been rewritten. You'll notice the cool new display but it's also much more reliable and efficient. Make sure to set jobs: to a value greater than 1 in ~/.opam/config in case you updated from an older version.
• The install/upgrade/downgrade/remove/reinstall actions are also processed in a better way: the consequences of a failed actions are minimised, when it used to abort the full command.
• When using version control to pin a package to a local directory without specifying a branch, only the tracked files are used by OPAM, but their changes don't need to be checked in. This was found to be the most convenient compromise.
• Sources used for several OPAM packages may use <name>.opam files for package pinning. URLs of the form git+ssh:// or hg+https:// are now allowed.
• opam lint has been vastly improved.

... and much more

There is also a new manual documenting the file and repository formats.

Fixes

See the changelog for a summary or closed issues in the bug-tracker for an overview.

Experimental features

These are mostly improvements to the file formats. You are welcome to use them, but they won't be accepted into the official repository until the next release.

• New field features: in opam files, to help with ./configure scripts and documenting the specific features enabled in a given build. See the original proposal and the section in the new manual
• The "filter" language in opam files is now well defined, and documented in the manual. In particular, undefined variables are consistently handled, as well as conversions between string and boolean values, with new syntax for converting bools to strings.
• New package flag "verbose" in opam files, that outputs the package's build script to stdout
• New field libexec: in <name>.install files, to install into the package's lib dir with the execution bit set.
• Compilers can now be defined without source nor build instructions, and the base packages defined in the packages: field are now resolved and then locked. In practice, this means that repository maintainers can move the compiler itself to a package, giving a lot more flexibility.