A non-hidden default source tree

[Faré]

Robert astutely noted that the absence of a default user source tree that isn't a hidden directory is a barrier to coding for new programmers: they have to either adopt one of the ugly XDG paths, or to modify their source registry.

There should

See this long discussion:
http://thread.gmane.org/gmane.lisp.asdf.devel/3851

Proposed names include:
~/lisp/ (is an actual hurdle to p-cos, a bit imprecise for casual users)
~/cl/ (a bit too familiar, but otherwise fine)
~/common-lisp/ (preferred by Faré, simple and self-documenting, not just for asdf)
~/asdf-local-projects/ (preferred by Robert(?), almost guaranteed to be new)

*Usually*, even if the directory already exists, there will be no meaningful clash:
1- the user already configured his ASDF to find his systems, so any defaults don't matter.
 Defaults mostly only matter to newbies and people who don't already have configured systems.
2- new defaults may shadow other lower-priority defaults, but it's hard to conceive
 that the user would specifically keep obsolete versions in ~/common-lisp/
 while at the same time having the system provide a newer one in /usr/share/common-lisp/
 and at the same time the user not having a yet non-obsolete one configured.
 The kind of user who would do that and not partake of the conversation on asdf-devel
 is probably non-existent.

Therefore, though I wouldn't use ~/lisp/ because of the known clash for p-cos as well as because the name doesn't distinguish between many kinds of lisps, I still recommend ~/common-lisp/ as this new default directory. I strongly dislike ~/asdf-local-projects/ because the ASDF source-registry directly descends from the original XCVB search-path, is shared between ASDF and XCVB, and may yet be used by future CL build tools different from ASDF. It's not just for ASDF, it's for all of common-lisp.

The way to add this new default would be to add a new function default-user-source-registry or such, that appears between user-source-registry-directory and system-source-registry in *default-source-registries*. Which raises the question of whether we want to bump *oldest-forward-compatible-asdf-version* or make defparameter* more clever and aware of a compatibility version.

The function itself would be defined as:
(defun default-user-source-registry () `(:source-registry (:tree (:home "common-lisp") :inherit-configuration))

[Robert P. Goldman (rpgoldman)]

I'm going to take point of personal privilege and bump the priority of this bug. I was writing the "quick start guide," and the current default location for easy placement of one's lisp code was just too embarrassing.

[Faré (fahree)]

Actually, what I would do is:

1- split default-source-registry into two parts:
   default-user-source-registry, after user-source-registry and user-source-registry-directory,
   and default-system-source-registry, after system-source-registry and system-source-registry-directory.

2- all user stuff go into default-user-source-registry, which seems to be everthing currently in default-source-registry, with exceptions below: XDG_DATA_HOME is for the user, but XDG_DATA_DIRS is for the system. local-appdata and appdata are for the user, but common-appdata is for the system.

3- then comes the issue of upgrade. defparameter* needs be enriched with some optional version thing, and only overwrite the previous value if upgrading from too old a version, which if not necessary older than *oldest-forward-compatible-asdf-version* (but defaulting to it). Instead of using a hook on *post-upgrade-cleanup-hook*, it should probably compare to the version, and overwrite if (version< actual-version-upgraded-from oldest-forward-compatible-asdf-version-for-this-variable).

[Faré (fahree)]

If you want me to do this upgrade surgery, just tell me what directory you want to make the default.

[Faré (fahree)]

Fixed in 3.1.0.102: ~/common-lisp/ is now in the default-user-source-registry.