feat: initial blink-cmp-ssh implementation

Problem: the existing blink-cmp-sshconfig plugin uses a synchronous,
build-time Python scraping approach that requires uv and make to
generate a static Lua file.

Solution: implement a runtime, async blink.cmp source that parses
ssh_config keywords from man ssh_config and enum values from ssh -Q
queries, matching the architecture of blink-cmp-tmux and
blink-cmp-ghostty.

spec/helpers.lua

@@ -0,0 +1,54 @@
+local plugin_dir = vim.fn.getcwd()
+vim.opt.runtimepath:prepend(plugin_dir)
+
+if not package.loaded['blink.cmp.types'] then
+  package.loaded['blink.cmp.types'] = {
+    CompletionItemKind = {
+      Text = 1,
+      Method = 2,
+      Function = 3,
+      Constructor = 4,
+      Field = 5,
+      Variable = 6,
+      Class = 7,
+      Interface = 8,
+      Module = 9,
+      Property = 10,
+      Unit = 11,
+      Value = 12,
+      Enum = 13,
+      Keyword = 14,
+      Snippet = 15,
+      Color = 16,
+      File = 17,
+      Reference = 18,
+      Folder = 19,
+      EnumMember = 20,
+      Constant = 21,
+      Struct = 22,
+      Event = 23,
+      Operator = 24,
+      TypeParameter = 25,
+    },
+  }
+end
+
+local M = {}
+
+function M.create_buffer(lines, filetype)
+  local bufnr = vim.api.nvim_create_buf(false, true)
+  vim.api.nvim_buf_set_lines(bufnr, 0, -1, false, lines or {})
+  if filetype then
+    vim.api.nvim_set_option_value('filetype', filetype, { buf = bufnr })
+  end
+  vim.api.nvim_set_current_buf(bufnr)
+  return bufnr
+end
+
+function M.delete_buffer(bufnr)
+  if bufnr and vim.api.nvim_buf_is_valid(bufnr) then
+    vim.api.nvim_buf_delete(bufnr, { force = true })
+  end
+end
+
+return M

spec/minimal_init.lua

@@ -0,0 +1,34 @@
+vim.cmd([[set runtimepath=$VIMRUNTIME]])
+vim.opt.runtimepath:append('.')
+vim.opt.packpath = {}
+vim.opt.loadplugins = false
+
+package.loaded['blink.cmp.types'] = {
+  CompletionItemKind = {
+    Text = 1,
+    Method = 2,
+    Function = 3,
+    Constructor = 4,
+    Field = 5,
+    Variable = 6,
+    Class = 7,
+    Interface = 8,
+    Module = 9,
+    Property = 10,
+    Unit = 11,
+    Value = 12,
+    Enum = 13,
+    Keyword = 14,
+    Snippet = 15,
+    Color = 16,
+    File = 17,
+    Reference = 18,
+    Folder = 19,
+    EnumMember = 20,
+    Constant = 21,
+    Struct = 22,
+    Event = 23,
+    Operator = 24,
+    TypeParameter = 25,
+  },
+}

spec/ssh_spec.lua

@@ -0,0 +1,183 @@
+local helpers = require('spec.helpers')
+
+local MAN_PAGE = table.concat({
+  'SSH_CONFIG(5)                  File Formats Manual                SSH_CONFIG(5)',
+  '',
+  '       The  possible keywords and their meanings are as follows:',
+  '',
+  '       Host    Restricts the following declarations (up to  the  next  Host  or',
+  '               Match keyword) to be only for those hosts that match one of the',
+  '               patterns given after the keyword.',
+  '',
+  '       StrictHostKeyChecking',
+  '               If this flag is set to yes, ssh(1) will never automatically add',
+  '               host keys to the ~/.ssh/known_hosts file, and refuses to connect',
+  '               to hosts whose host key has changed.',
+  '',
+  '       Hostname',
+  '               Specifies the real host name to log into.',
+  '',
+}, '\n')
+
+local SSH_Q_OUTPUT = table.concat({
+  '##cipher',
+  'aes128-ctr',
+  'aes256-ctr',
+  'chacha20-poly1305@openssh.com',
+  '##cipher-auth',
+  'chacha20-poly1305@openssh.com',
+  '##mac',
+  'hmac-sha2-256',
+  '##kex',
+  'curve25519-sha256',
+  '##key',
+  'ssh-ed25519',
+  '##key-cert',
+  '##key-plain',
+  '##key-sig',
+  'ssh-ed25519',
+  '##protocol-version',
+  '2',
+  '##compression',
+  'none',
+  'zlib@openssh.com',
+  '##sig',
+}, '\n')
+
+local function mock_system()
+  local original_system = vim.system
+  local original_schedule = vim.schedule
+  ---@diagnostic disable-next-line: duplicate-set-field
+  vim.system = function(cmd, _, on_exit)
+    local stdout = ''
+    if cmd[1] == 'bash' and cmd[3] and cmd[3]:find('man %-P cat ssh_config') then
+      stdout = MAN_PAGE
+    elseif cmd[1] == 'bash' and cmd[3] and cmd[3]:find('ssh %-Q') then
+      stdout = SSH_Q_OUTPUT
+    end
+    local result = { stdout = stdout, code = 0 }
+    if on_exit then
+      on_exit(result)
+      return {}
+    end
+    return {
+      wait = function()
+        return result
+      end,
+    }
+  end
+  vim.schedule = function(fn)
+    fn()
+  end
+  return function()
+    vim.system = original_system
+    vim.schedule = original_schedule
+  end
+end
+
+describe('blink-cmp-ssh', function()
+  local restores = {}
+
+  before_each(function()
+    package.loaded['blink-cmp-ssh'] = nil
+  end)
+
+  after_each(function()
+    for _, fn in ipairs(restores) do
+      fn()
+    end
+    restores = {}
+  end)
+
+  describe('enabled', function()
+    it('returns true for sshconfig filetype', function()
+      local bufnr = helpers.create_buffer({}, 'sshconfig')
+      local source = require('blink-cmp-ssh')
+      assert.is_true(source.enabled())
+      helpers.delete_buffer(bufnr)
+    end)
+
+    it('returns false for other filetypes', function()
+      local bufnr = helpers.create_buffer({}, 'lua')
+      local source = require('blink-cmp-ssh')
+      assert.is_false(source.enabled())
+      helpers.delete_buffer(bufnr)
+    end)
+  end)
+
+  describe('get_completions', function()
+    it('returns keyword items with Property kind on empty line', function()
+      restores[#restores + 1] = mock_system()
+      local source = require('blink-cmp-ssh').new()
+      local items
+      source:get_completions({ line = '', cursor = { 1, 0 } }, function(response)
+        items = response.items
+      end)
+      assert.is_not_nil(items)
+      assert.equals(3, #items)
+      for _, item in ipairs(items) do
+        assert.equals(10, item.kind)
+      end
+    end)
+
+    it('returns keyword items on partial keyword', function()
+      restores[#restores + 1] = mock_system()
+      local source = require('blink-cmp-ssh').new()
+      local items
+      source:get_completions({ line = 'Str', cursor = { 1, 3 } }, function(response)
+        items = response.items
+      end)
+      assert.is_not_nil(items)
+      assert.equals(3, #items)
+    end)
+
+    it('includes man page documentation in items', function()
+      restores[#restores + 1] = mock_system()
+      local source = require('blink-cmp-ssh').new()
+      local items
+      source:get_completions({ line = '', cursor = { 1, 0 } }, function(response)
+        items = response.items
+      end)
+      local strict = vim.iter(items):find(function(item)
+        return item.label == 'StrictHostKeyChecking'
+      end)
+      assert.is_not_nil(strict)
+      assert.is_not_nil(strict.documentation)
+      assert.is_truthy(strict.documentation.value:find('known_hosts'))
+    end)
+
+    it('returns enum values after a known keyword', function()
+      restores[#restores + 1] = mock_system()
+      local source = require('blink-cmp-ssh').new()
+      local items
+      source:get_completions(
+        { line = 'StrictHostKeyChecking ', cursor = { 1, 22 } },
+        function(response)
+          items = response.items
+        end
+      )
+      assert.is_not_nil(items)
+      assert.is_true(#items > 0)
+      for _, item in ipairs(items) do
+        assert.equals(20, item.kind)
+      end
+    end)
+
+    it('returns empty after a non-enum keyword', function()
+      restores[#restores + 1] = mock_system()
+      local source = require('blink-cmp-ssh').new()
+      local items
+      source:get_completions({ line = 'Hostname ', cursor = { 1, 9 } }, function(response)
+        items = response.items
+      end)
+      assert.equals(0, #items)
+    end)
+
+    it('returns a cancel function', function()
+      restores[#restores + 1] = mock_system()
+      local source = require('blink-cmp-ssh').new()
+      local cancel = source:get_completions({ line = '', cursor = { 1, 0 } }, function() end)
+      assert.is_function(cancel)
+    end)
+  end)
+end)