Simplify Go Endpoints + Add Tests (#120)

This MR represents a major refactor of the Go codebase, as well as introducing tests for the handlers. The MR also introduces an endpoint to shutdown or restart the Go server, which may be useful for clients who want to refresh the state of the plugin after checking out branches. Finally, this MR adds a contributing document for users who want to make feature changes.

lua/gitlab/server.lua

@@ -3,6 +3,7 @@
 -- to Gitlab and returning the data
 local state = require("gitlab.state")
 local u = require("gitlab.utils")
+local job = require("gitlab.job")
 local M = {}
 
 -- Starts the Go server and call the callback provided
@@ -60,7 +61,12 @@ M.start = function(callback)
       end
     end,
     on_exit = function(job_id, exit_code)
-      u.notify("Golang gitlab server exited: job_id: " .. job_id .. ", exit_code: " .. exit_code, vim.log.levels.ERROR)
+      if exit_code ~= 0 then
+        u.notify(
+          "Golang gitlab server exited: job_id: " .. job_id .. ", exit_code: " .. exit_code,
+          vim.log.levels.ERROR
+        )
+      end
     end,
   })
   if job_id <= 0 then
@@ -95,4 +101,41 @@ M.build = function(override)
   return true
 end
 
+-- Shuts down the Go server and clears out all old gitlab.nvim state
+M.shutdown = function(cb)
+  if not state.go_server_running then
+    vim.notify("The gitlab.nvim server is not running", vim.log.levels.ERROR)
+    return
+  end
+  job.run_job("/shutdown", "POST", { restart = false }, function(data)
+    state.go_server_running = false
+    state.clear_data()
+    if cb then
+      cb()
+    else
+      u.notify(data.message, vim.log.levels.INFO)
+    end
+  end)
+end
+
+-- Restarts the Go server and clears out all gitlab.nvim state
+M.restart = function(cb)
+  if not state.go_server_running then
+    vim.notify("The gitlab.nvim server is not running", vim.log.levels.ERROR)
+    return
+  end
+  job.run_job("/shutdown", "POST", { restart = true }, function(data)
+    state.go_server_running = false
+    M.start(function()
+      state.go_server_running = true
+      state.clear_data()
+      if cb then
+        cb()
+      else
+        u.notify(data.message, vim.log.levels.INFO)
+      end
+    end)
+  end)
+end
+
 return M