commit fd5a52a5d8b7d9e40debc473d5799bfafb8c60db
author Derek Che <drc@yahoo-inc.com> Thu Dec 18 21:22:47 2014 -0800
committer Adam Langley <agl@golang.org> Fri Dec 19 22:48:49 2014 +0000
tree fa6b1b60351effb396b583424e6083d708ed7ada
parent 3c38914b08f12b27bff0ad2105b42ef4c65a9461

ssh/terminal: fix SetSize when nothing on current line

SetSize has a problem may cause the following ReadPassword setting
temporary prompt not working, when changing width the current
SetSize will call clearAndRepaintLinePlusNPrevious which would
print an old prompt whatever the current line has, causing a following
ReadPassword with temporary prompt not printing the different prompt.

When running code like this, the nt.SetSize prints a "> " as
prompt then the temporary "Password: " prompt would never show up.

```go
        oldState, err := terminal.MakeRaw(int(os.Stdin.Fd()))
        width, height, _ = terminal.GetSize(int(os.Stdin.Fd()))
        nt := terminal.NewTerminal(os.Stdin, "> ")
        nt.SetSize(width, height)
        password, err = nt.ReadPassword("Password: ")
```

the new test cases is to test SetSize with different terminal sizes,
either shrinking or expanding, a following ReadPassword should get the
correct temporary prompt.

Change-Id: I33d13b2c732997c0c88670d53545b8c0048b94b6
Reviewed-on: https://go-review.googlesource.com/1861
Reviewed-by: Adam Langley <agl@golang.org>