Problem: Some use cases require or benefit from persistent on disk
storage of plugin data (a.k.a. "lockfile"):
1. Allow `update()` to act on not-yet-active plugins. Currently if
`add()` is not yet called, then plugin's version is unknown
and `update()` can't decide where to look for changes.
2. Efficiently know plugin's dependencies without having to read
'pkg.json' files on every load for every plugin. This is for the
future, after there is `packspec` support (or other declaration of
dependencies on plugin's side).
3. Allow initial install to check out the exact latest "working" state
for a reproducible setup. Currently it pulls the latest available
`version.`
4. Ensure that all declared plugins are installed, even if lazy loaded.
So that later `add()` does not trigger auto-install (when there
might be no Internet connection, for example) and there is no issues
with knowing which plugins are used in the config (so even never
loaded rare plugins are still installed and can be updated).
5. Allow `add()` to detect if plugin's spec has changed between
Nvim sessions and act accordingly. I.e. either set new `src` as
origin or enforce `version.` This is not critical and can be done
during `update()`, but it might be nice to have.
Solution: Add lockfile in JSON format that tracks (adds, updtes,
removes) necessary data for described use cases. Here are the required
data that enables each point:
1. `name` -> `version` map.
2. `name` -> `dependencies` map.
3. `name` -> `rev` map. Probably also requires `name` -> `src` map
to ensure that commit comes from correct origin.
4. `name` -> `src` map. It would be good to also track the order,
but that might be too many complications and redundant together
with point 2.
5. Map from `name` to all relevant spec fields. I.e. `name` -> `src`
and `name` -> `version` for now. Storing data might be too much,
but can be discussed, of course.
This commit only adds lockfile tracking without implementing actual
use cases. It is stored in user's config directory and is suggested to
be tracked via version control.
Example of a lockfile:
```json
{
# Extra nesting to more future proof.
"plugins": {
"plug-a": {
"ref": "abcdef1"
"src": "https://github.com/user/plug-a",
# No `version` means it was `nil` (infer default branch later)
},
"plug-b": {
"dependencies": ["plugin-a", "plug-c"],
"src": "https://github.com/user/plug-b",
"ref": "bcdefg2",
# Enclose string `version` in quotes
"version": "'dev'"
},
"plug-c": {
"src": "https://github.com/user/plug-c",
"ref": "cdefgh3",
# Store `vim.version.Range` via its `tostring()` output
"version": ">=0.0.0",
}
}
}
```
d7db552394