Document update-lockfile limitations

[rarkins]

Describe the proposed change(s).

rangeStrategy=update-lockfile means that we have the ability to keep the package file the same, but update the locked version only. Per our docs:

Works for bundler, cargo, composer, gleam, npm, yarn, pnpm, terraform and poetry so far

(this list may be incomplete)

The problem is that not all of these managers support exact lock file updating. Some just let you say "update package foo" and it will usually update to the latest version in the allowed range, not necessarily the version users want Renovate to update to. The version to update to is often not the latest in the allowed range because of things like:

• separateMinorPatch
• minimumReleaseAge

For this task:

• Check that the list above is correct
• For each of these, document which support "exact" lockfile updating (e.g. update package foo to v1.2.3 exactly) versus which just say "update package foo to latest"

We then may need to decide how to handle these differences programmatically

[zharinov]

Looks like lockFileMaintenance must be used instead:

renovate/docs/usage/ruby.md

Line 19 in f478e1d

When using `"rangeStrategy": "update-lockfile"`, all gems listed in the `Gemfile` will be updated, even if they do not have a version specified.