Create a Permissions class

To make #1156 less of a mess, create a Permissions class to allow for

• Type safety - can be parsed from a String instead of an int to avoid octal vs. decimal confusion
• Compactness - internal representation can still be an int
• Ease of use - relevant methods on this class instead of using a helper and doing multiple back-and-forth conversions
• Extendability - should be easy to add operations if/as we need them

Right now we only really need two methods:

/* Parse/validate an octal String (e.g. "755"). */
static Permissions fromString(String octalString);

/* Set the permissions on a TarArchiveEntry. */
void setOnTarArchiveEntry(TarArchiveEntry entry);

but we can decide to add stuff depending on how people want to use the library.

static Permissions fromSet(Set<PosixFilePermission> octalString);

Permissions addPermission(PosixFilePermission permission);

Set<PosixFilePermission> getPermissionSet();

int getPermissionBits();

// etc.

[coollog]

Yea, this class will be user-facing, so getPermissionBits sounds good instead of requiring TarArchiveEntry.

[TadCordle]

One thing I’m not so thrilled about is that it has a dependency on some particular external library (Apache Commons Compress). May not matter much if this is exclusively for internal usage.

That’s true. I don’t think this class is going to be exclusively for internal usage. It might be worth it to just leave out applyToTarArchiveEntryMode and use getPermissionBits.

Alternatively, we could make it applyToFileMode which would take an int and return an int with the lowest 9 bits set.