Use placeholders in progress messages

[fmeum]

This allows Bazel to render the labels in progress messages in a more user-friendly way by unmapping mapped repository names to the names used by the main repository, which is especially relevant with Bzlmod.

[restingbull]

Where is the documentation on this?

[fmeum]

It's documented in https://bazel.build/rules/lib/actions#run (see the progress_message parameter) and has been added in bazelbuild/bazel@bfa3643, which means that it is available in Bazel 5.0.0 and later.

[Bencodes]

which means that it is available in Bazel 5.0.0 and later.

@fmeum what happens on versions prior to 5.x? Would we need to bump the minimum supported version of rules_kotlin up to 5.x, dropping 4.x?

[fmeum]

@Bencodes With Bazel 4, users would see the literal string %{label} instead of the label. Given that Bazel 6 is out now, it may be a good time to raise the minimum version, but not if this PR is the only reason to do so. It isn't fixing an important issue, just making progress messages a little nicer with Bazel 6 as well as Bzlmod.

[Bencodes]

@Bencodes With Bazel 4, users would see the literal string %{label} instead of the label. Given that Bazel 6 is out now, it may be a good time to raise the minimum version, but not if this PR is the only reason to do so. It isn't fixing an important issue, just making progress messages a little nicer with Bazel 6 as well as Bzlmod.

I'm not against dropping support for 4.x after we cut a final 1.7.0 release of rules_kotlin, which we can do this week.

[restingbull]

Will need to announce bzl 4 removal.

[Bencodes]

#903 (comment)