[feature request] generate UNIX extra fields

[dduponchel]

Keeping the "version made by" flag in the directory record to "DOS" sounds good, but we lack a way to change it to "UNIX" for example and add extra fields to set the unix permissions. Setting executable files will be useful, see sindresorhus/gulp-zip#38.
The field "external file attributes" will also need some investigations (when generating or parsing) as it depends on the "version made by" field.

[dduponchel]

The unix permissions are stored in the "external file attributes" (this link was really useful). Generating / parsing this field is easy but we need to be careful with what we allow in the API.

I though that a field permissions with a string ("644" or "755") or the nodejs stats.mode field would be enough. On nodejs/windows, a folder will get "444" or "666" from stats.mode (after conversion) and this permissions on a folder will render it unusable on linux/mac. Not good.

Moreover the DOS files attributes are still used (I'm still investigating the windows ACL support) : we could support them too. If I follow wikipedia, Info-ZIP does a mapping between the two which can lead to broken things so I'd rather not try to mix them together.

I suggest the follow API :

• generate() gains a new option : platform ("DOS", "UNIX" or nodejs process.platform)
• ZipObject gains two new objects : dosPermissions and unixPermissions. They are null unless defined when adding a file with specific permissions (manually or when parsing a zip file). They contains platform specific fields :
  • hidden, readOnly for dos
  • executable, readOnly for unix

The other solution I see is to completely expose the "external file attributes" : easier for us but the user will need to know exactly how to generate it.