fix: refuse a forced tty where sftp and captured output run

lua/sshfs/lib/ssh.lua

@@ -50,7 +50,11 @@ local function get_ssh_options(auth_type)
 
   -- A config RemoteCommand cannot coexist with the command these paths append,
   -- and sftp needs a plain session, so it is cleared for everything but a shell.
-  if auth_type == "batch" or auth_type == "socket" then table.insert(options, "RemoteCommand=none") end
+  if auth_type == "batch" or auth_type == "socket" then
+    table.insert(options, "RemoteCommand=none")
+    -- A forced tty closes the sftp channel and puts carriage returns in captured output.
+    table.insert(options, "RequestTTY=no")
+  end
 
   -- Add ControlMaster options
   local control_opts = Config.get_control_master_options()

tests/remote_command_spec.lua

@@ -23,6 +23,26 @@ local function clears_remote_command(cmd)
   return option_index(cmd, "RemoteCommand=none") ~= nil
 end
 
+describe("RequestTTY handling", function()
+  it("refuses a forced tty on the paths that carry sftp or captured output", function()
+    local Ssh = load_ssh()
+
+    expect.truthy(option_index(Ssh.build_batch_command("example.com"), "RequestTTY=no"))
+    expect.truthy(option_index(Ssh.build_home_command("example.com"), "RequestTTY=no"), "readlink output must be clean")
+    expect.contains(Ssh.build_command_string("socket"), "-o RequestTTY=no")
+  end)
+
+  it("leaves the interactive authentication terminal a tty", function()
+    local Ssh = load_ssh()
+    expect.is_nil(option_index(Ssh.build_auth_command("example.com"), "RequestTTY=no"), "a password prompt needs one")
+  end)
+
+  it("leaves a terminal session a tty", function()
+    local Ssh = load_ssh()
+    expect.is_nil(option_index(Ssh.build_command("example.com", "/srv/app"), "RequestTTY=no"))
+  end)
+end)
+
 describe("RemoteCommand handling", function()
   it("clears it on every command that appends a remote command", function()
     local Ssh = load_ssh()

tests/ssh_spec.lua

@@ -13,7 +13,7 @@ end
 describe("Ssh.build_command_string", function()
   it("passes the control path and clears any RemoteCommand when reusing a socket", function()
     local Ssh = load_ssh()
-    expect.eq(Ssh.build_command_string("socket"), "ssh -o RemoteCommand=none -o " .. CONTROL_PATH)
+    expect.eq(Ssh.build_command_string("socket"), "ssh -o RemoteCommand=none -o RequestTTY=no -o " .. CONTROL_PATH)
   end)
 
   it("forces a master and disables prompts for batch connections", function()