title: zip two file with same content, but final md5sum is different
body: <p>I have the following operation on my mac:</p>
  
  <pre><code>$ echo "dgrgrrgrgrg" &gt; test1.txt
  </code></pre>
  
  <p>after a few seconds, copy test1.txt:</p>
  
  <pre><code>$ cp test1.txt test2.txt
  $ ls -l
  total 16
  -rw-r--r--  1 hqfy  staff  12 Mar 31 10:18 test1.txt
  -rw-r--r--  1 hqfy  staff  12 Mar 31 10:19 test2.txt
  </code></pre>
  
  <p>now chech md5sum:</p>
  
  <pre><code>$ md5 *.txt
  MD5 (test1.txt) = 8bab5a3e202c901499d83cb25d5a8c80
  MD5 (test2.txt) = 8bab5a3e202c901499d83cb25d5a8c80
  </code></pre>
  
  <p>it's obvious that test1.txt and test2.txt have the same md5sum, now I zip these two files:</p>
  
  <pre><code>$ zip -X test1.zip test1.txt
      adding: test1.txt (deflated 8%)
  $ zip -X test2.zip test2.txt
      adding: test2.txt (deflated 8%)
  $ ls -l
  total 32
  -rw-r--r--  1 hqfy  staff   12 Mar 31 10:18 test1.txt
  -rw-r--r--  1 hqfy  staff  127 Mar 31 10:22 test1.zip
  -rw-r--r--  1 hqfy  staff   12 Mar 31 10:19 test2.txt
  -rw-r--r--  1 hqfy  staff  127 Mar 31 10:23 test2.zip
  </code></pre>
  
  <p>size of test1.zip and test2.zip are the same, but when I check md5sum:</p>
  
  <pre><code>$ md5 *.zip
  MD5 (test1.zip) = af8783f96ce98aef717ecf6229ffb07e
  MD5 (test2.zip) = 59e752a03a2930adbe7f30b9cbf14561
  </code></pre>
  
  <p>I've googled it, using zip with option -X, but it did not work in my case, how can I create the two zip files with the same md5sum?</p>