fix(pack): recover from broken HEAD repos during startup

lua/plugins/pack.lua

@@ -1,5 +1,28 @@
 local M = {}
 
+local function has_valid_head(path)
+    if vim.fn.isdirectory(path .. "/.git") == 0 then
+        return true
+    end
+
+    vim.fn.system({ "git", "-C", path, "rev-parse", "--verify", "HEAD" })
+    return vim.v.shell_error == 0
+end
+
+local function prune_broken_pack_repos()
+    local root = vim.fn.stdpath("data") .. "/site/pack/core/opt"
+    if vim.fn.isdirectory(root) == 0 then
+        return
+    end
+
+    for _, dir in ipairs(vim.fn.readdir(root)) do
+        local path = root .. "/" .. dir
+        if vim.fn.isdirectory(path) == 1 and not has_valid_head(path) then
+            vim.fn.delete(path, "rf")
+        end
+    end
+end
+
 local function to_src(value)
     if value:match("^[%w+.-]+://") or value:match("^git@") then
         return value
@@ -21,7 +44,23 @@ function M.add(specs)
         end
     end
 
-    vim.pack.add(resolved, { confirm = false, load = true })
+    local ok, err = pcall(vim.pack.add, resolved, { confirm = false, load = true })
+
+    if not ok and tostring(err):find("ambiguous argument 'HEAD'", 1, true) then
+        prune_broken_pack_repos()
+        vim.fn.delete(vim.fn.stdpath("config") .. "/nvim-pack-lock.json")
+        ok, err = pcall(vim.pack.add, resolved, { confirm = false, load = true })
+    end
+
+    if not ok then
+        vim.schedule(function()
+            local msg = "vim.pack failed to install/load plugins. Check network and run :lua vim.pack.update()."
+            vim.notify(msg .. "\n" .. tostring(err), vim.log.levels.WARN)
+        end)
+        return false
+    end
+
+    return true
 end
 
 return M