feature: Workspace data dir should be unique #54

Did you check the docs?

• I have read all the docs

Is your feature request related to a problem? Please describe.

Currently jdtls is launched with something like -data /home/jvalkealahti/.cache/nvim/jdtls/workspaces/common-workspace. All the examples around jdtls seems to propose to just use a common directory which imho is just wrong. When you re-launch jdtls or used a completely different project, jdtls will actually partially wipe stuff from its data directory.

That's why i.e. vscode will calculate a hash(based on your project root) and uses that to launch jdtls with unique data directory.

Describe the solution you'd like

In my nvim-jdtls setup i've just been using this relatively naive hack which with this plugin would look something like:

local project_name = string.gsub(vim.fn.fnamemodify(vim.fn.getcwd(), ":p:h"), "/", "_")
local path = join(cache_dir, 'nvim', 'jdtls', 'workspaces', 'common-workspace', project_name)

That would give you something like /home/jvalkealahti/.cache/nvim/jdtls/workspaces/common-workspace/_home_jvalkealahti_path_to_projectroot.

Lua don't have any buildin hash functions so we'd just need to come up with something else which creates a unique directory name.

Describe alternatives you've considered

Don't there's any.

Additional context

No response