Support TryExec key like in .desktop files

[Sergey "Shnatsel" Davidoff]

Contractor should support a TryExec key like in .desktop files, see http://standards.freedesktop.org/desktop-entry-spec/latest/ar01s05.html

This is an extension of bug 912413 required for properly handling contracts that use an wrapper over the actual provider - which will happen very often, as far as I can tell.

[Victor Martinez (victored)]

This is good and easy to implement but at the same time it encourages bad/lazy system integration. Package dependencies should do it. A "wont fix" IMHO.

[Victor Martinez (victored)]

I'd like to be proven wrong though :)

[Sergey "Shnatsel" Davidoff (shnatsel)]

Example: Inkscape. It requires a wrapper script for contracts to function properly, but the presence of the script does not guarantee the presence of Inkscape. In theory it should, BUT unfortunately there's no way we can make installing Inkscape also install the package with contracts. So until we upstream the contracts we have 3 options:
1) Let the user discover the existence of a separate contracts package and install it manually (not realistic)
2) Patch Inkscape package to either include the contracts or recommend the contracts package (cumbersome)
3) Check presence of actual Inkscape binary from TryExec=

[Victor Martinez (victored)]

I added initial support for TryExec to fix another bug by the way.