.install files and executable bit

[dbuenzli]

Currently we have:

File permissions are set to 0644, except for libexec, bin, sbin, stublibs for 
which it’s 0755. umask may apply.

Is there a strong reason in doing so ?

This is quite annoying for some software I'm developing. I'm storing arbitary files in the etc directory of a package. These files can be copied over somewhere else on user request, but the executable bit of these file is an important bit of information.

So my proposal would be to always preserve the executable bit, whatever the section.

[dbuenzli]

Other use case would include having sample ocaml scripts for a library in a share or doc directory.

[AltGr]

This originally mimicked the behaviour of the UNIX install command; not sure it's strictly needed, but it may help with files coming from a filesystem or archive without file permissions. Another option would be a way to specify the desired permissions in the .install file.

[dra27]

It's hard to see what the story could be for compatibility for this change - it could conceivably be done by having a package flag to opt-in to a perms-preserving installation, but this couldn't be relied on without constraining a package to a newer opam client (and that also wouldn't work if using opam-installer directly). It can - at least for the foreseeable future - be done with manual installation commands. Is this still an issue, or can this can be closed, therefore?

[dbuenzli]

I think it could be, you may want to install scripts in share that you don't want to have in bin. But in that case the package can install the files itself rather than rely on .install files.