I've gone backwards and forwards on the design for dependency version
management. However, I think what's written in this commit represents
a pretty sane "sweet spot" between all available options.
In a nutshell, anytime reference to a stack type in your Mufile is a
full-blown StackRef; in other words, it has a protocol (e.g., "https://"),
a base URL (e.g., "hub.mu.com/"), a name (e.g., "aws/s3/bucket"), and a
version ("@^1.0.6"). Each reference carries all of these components.
For convenience, you may omit the components. In that case, Mu chooses
reasonable defaults:
* "https://" as the default protocol (or "git://"; this is TBD).
* "hub.mu.com/" as the default base URL.
* "@latest" as the default version number.
Note that a version can be "latest" to mean "tip", a specific SHA hash
to pin to a precise version, or a semantic version number/range.
I had originally shied away from specifying versions inline as you reference
stacks in your Mufile, and was leaning towards an explicit dependencies
section, however I was swayed for two reasons:
1. It's very common to only consume a given stack once in a file. Needing
to specify it in two places each time is verbose and violates DRY.
2. We have decided that each Mufile stands on its own and forms the unit
of distribution. I had previously thought we might move dependencies
out of Mufiles into a "package manager" specification. Lacking that,
there is even less reason to call them out in a dedicated section.
Now, managing all these embedded version numbers across multiple stacks in
a single workspace would have been annoying. (Many edits for a single
version bump.) Instead, I've added provisions for storing this in your
workspace.yaml file. The way it works is if any StackRef lacks a version
number, before defaulting to "@latest" we check the workspace.yaml file and,
if a default is found in there, we will use it. For example:
dependencies:
aws/s3/bucket: ^1.0.6
The provision for pinning an entire namespace is also preserved. E.g.:
dependencies:
aws/...: ^1.0.6
This changes the probing logic for dependency resolution. The old logic was
inconsistent between the various roots. The new approach simply prefers locations
with a base URL component -- since they are more specific -- but will allow for
locations missing a base URL component. This is convenient for developers managing
a workspace where needing to specify the base URL in the path is annoying and
slightly too "opinionated" for my taste (especially for migrating existing services).
We will use the $MUROOT envvar to determine where Mu has been installed,
which will by default be /usr/local/mu. From there, we can access the
predefined library of stacks (underneath $MUROOT/bin/stacks).
