kiss: Support two-way symlinked dependencies.

[dylanaraps]

Related #163

@konimex Please let me know your opinion on this.

Correctly handles:

• gzip (installed) (symlink to) pigz (depends)
• gzip (depends) (symlink to) pigz (installed)
• Anything else to try?

TODO:

• [ ] Package manager must also update depends files to reflect the change (similar to fixdeps()).

[konimex]

Have you tested the case if there are more than one dependency (and possibly more than one "provides" in a dependency file)?

Also:

Package manager must also update depends files to reflect the change (similar to fixdeps()).

This should be done on $pkg_db, right?

Otherwise, looks good.

[dylanaraps]

Have you tested the case if there are more than one dependency (and possibly more than one "provides" in a dependency file)?

Yes. Works fine.

This should be done on $pkg_db, right?

Yup.

[konimex]

Alright. I don't have any more test case so that looks good from me. :+1:

[dylanaraps]

Also turns out that this requires no further code for installation to fully function. It does require code in pkg_remove (Example: pigz is removable even if it is a runtime dependency for busybox as it depends on gzip).

[dylanaraps]

This turned out to be unworkable. Working on another method now. (Syncing up removal/install dependencies is difficult).