Interrupting (Ctrl-C) jpegtran causes data loss when -outfile points to input file

[Jani Uusitalo]

For optimizing files in-place with jpegtran, especially from scripts and when dealing with lots of pictures, it's handy to be able to specify input file as -outfile.

But there's a catch:

Steps to reproduce:
0. Have a large JPEG file, or, alternatively, somewhat slow CPU
1. `jpegtran -optimize -copy all -perfect -outfile large.jpg large.jpg`
2. Hit Ctrl-C before the command finishes

Result:
You now have a broken large.jpg with only part, if any, of the image data remaining.

What I expect to happen:
To have large.jpg as it was before I invoked jpegtran.

Workarounds:
Obviously the traditional workaround of specifying an intermediate temporary output file, then replacing the original with the temporary file only once jpegtran has finished.

ProblemType: Bug
DistroRelease: Ubuntu 16.04
Package: libjpeg-turbo-progs 1.4.2-0ubuntu3
ProcVersionSignature: Ubuntu 4.8.0-53.56~16.04.1-generic 4.8.17
Uname: Linux 4.8.0-53-generic x86_64
ApportVersion: 2.20.1-0ubuntu2.6
Architecture: amd64
CurrentDesktop: Unity
Date: Thu May 25 17:16:16 2017
InstallationDate: Installed on 2016-10-13 (224 days ago)
InstallationMedia: Ubuntu-Server 16.04.1 LTS "Xenial Xerus" - Release amd64 (20160719)
SourcePackage: libjpeg-turbo
UpgradeStatus: No upgrade log present (probably fresh install)