From 2d32a2965a5dbd5d299a277ebc75b07b2c186090 Mon Sep 17 00:00:00 2001
From: Andy Stewart <boss@airbladesoftware.com>
Date: Mon, 12 Feb 2018 16:32:43 +0000
Subject: [PATCH] Improve hunk previewing.

- Treat &previewheight as a maximum height.
- Make preview window shrink to fit the hunk.
- Resize preview window each time.
- Make preview window readonly and nomodifiable.

Based on code by @somini.  Thanks!

See #451.
---
 autoload/gitgutter/hunk.vim | 14 +++++++++++---
 1 file changed, 11 insertions(+), 3 deletions(-)

diff --git a/autoload/gitgutter/hunk.vim b/autoload/gitgutter/hunk.vim
index fd8de80..31e500b 100644
--- a/autoload/gitgutter/hunk.vim
+++ b/autoload/gitgutter/hunk.vim
@@ -196,15 +196,23 @@ endfunction
 
 
 function! s:preview(hunk_diff)
+  let hunk_lines = split(s:discard_header(a:hunk_diff), "\n")
+  let hunk_lines_length = len(hunk_lines)
+  let previewheight = min([hunk_lines_length, &previewheight])
+
   silent! wincmd P
   if !&previewwindow
-    noautocmd execute 'bo' &previewheight 'new'
+    noautocmd execute 'bo' previewheight 'new'
     set previewwindow
+  else
+    execute 'resize' previewheight
   endif
 
-  setlocal noro modifiable filetype=diff buftype=nofile bufhidden=delete noswapfile
+  setlocal noreadonly modifiable filetype=diff buftype=nofile bufhidden=delete noswapfile
   execute "%delete_"
-  call append(0, split(s:discard_header(a:hunk_diff), "\n"))
+  call append(0, hunk_lines)
+  normal! gg
+  setlocal readonly nomodifiable
 
   noautocmd wincmd p
 endfunction