title: What is the differences between `git stash show` and `git show`?
body: <p>I can view stashed changes as:</p>
  
  <pre><code>$ git stash show -p stash@{0}
  diff --git a/t/database/test.t b/t/database/test.t
  index 3e9dcf87..4326d7e0 100644
  --- a/t/database/test.t
  +++ b/t/database/test.t
  @@ -249,6 +249,8 @@ begin
       loop raise notice ''before: %%'', r; end loop;
     end if;
  
  +  -- delete OLD if NEW.sys_period is empty
  +  -- or create pid to track full version history. See transaction time
     UPDATE %1$s
     SET
       -- NOTICE: Here new values for sys_time column should be now() instead of sys_time()
  </code></pre>
  
  <p>But when I do <code>git show stash@{0}</code> or <code>git show -p 803d7231</code> it displays just info without changes:</p>
  
  <pre><code>commit 803d7231aebc79819d69b5e8505c4be7f747441f (refs/stash)
  Merge: 2b30b862 3f34d241
  Author: Eugen Konkov &lt;kes-kes@yandex.ru&gt;
  Date:   Mon Apr 27 12:34:43 2020 +0300
  
      On bi-temporal: TODO: Bi-Temporal improvement: track how data is changed
  </code></pre>
  
  <p>Why <code>git show</code> does not display diff?</p>