Avoid creating temp files during manifest injection

[mizdebsk]

JDK seems to create temp files with umask 077, which results in wrong permissions on some installed files. See rhbz#1579236 for the original bug report.

This PR reverts to in-place manifest injection. JAR file is first opened, then unlinked, but i-node and file contents remain on disk. Then new file (new i-node) is created with the old name and new data written into it. This avoids creating any temporary files.

CC @mbooth101

[codecov-io]

Codecov Report

Merging #31 into master will decrease coverage by <.01%.
The diff coverage is 100%.

@@             Coverage Diff              @@
##             master      #31      +/-   ##
============================================
- Coverage     77.71%   77.71%   -0.01%     
  Complexity      253      253              
============================================
  Files           101      101              
  Lines          4470     4469       -1     
  Branches        716      716              
============================================
- Hits           3474     3473       -1     
  Misses          684      684              
  Partials        312      312

Impacted Files	Coverage Δ	Complexity Δ
...org/fedoraproject/xmvn/tools/install/JarUtils.java	79.12% <100%> (-0.23%)	0 <0> (ø)

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[mizdebsk]

Sigh, I just realized this causes data loss (original JAR is removed) in case of some exception during JAR processing, so I probably should add a test case for this and further improve the code.

[msimacek]

Sigh, I just realized this causes data loss (original JAR is removed) in case of some exception during JAR processing, so I probably should add a test case for this and further improve the code.

That's the reason why I added the temporary file, because overwiting the JAR in place made debugging the original problem (jar corruption) quite painful. What about making the temporary file, but instead of using Files.move, copying the file content (after tmp file is done, open original with trunc and write the contents of tmp file into it, then delete tmp)?