[GSoC] Google Summer of Code 2009 - new ideas

Time to submit application as mentoring organization to Google Summer of Code 2009 is close: March 9 -- March 13.

I'd like to add a few ideas to SoC2009Ideas wiki page, but before I do this I'd like to ask for comments. (The proposals also lacks proposed mentor).

I am wondering if it would be worth it to make a separate class between "New to Git?" easy tasks, and "Larger Projects" hard tasks...

BTW. some of ideas didn't make it from SoC2008Ideas wiki page to current 
year page, namely: 
 * Apply sparse To Fix Errors
 * Lazy clone / remote alternates
 * Implement git-submodule using .gitlink file
 * Teach git-apply the 3-way merge fallback git-am knows
 * Better Emacs integration
Was this ommision deliberate or accidental?

-- >8 --

= New To Git? New To Open Source Development? =

== Packfile caching for git-daemon ==

Even with delta reuse, enumerating objects to be present in packfile generates significant load on server for pack-generating protocols, such as git:// protocol used by git-daemon. Many of requests result in the same packfile to be generated and sent; examples include full clone, or fetch of all branches since last update. It would make sense then to save (cache) packfiles, and if possible avoid regenerating packfiles by sending them from cache. (Possible extension would be to send slightly larger pack than needed if one can reuse cached packfile instead).

The goal is for git-daemon to cache packfiles, use cached packfiles if possible, and to manage packfile cache. Note that one would need in the final version some way to specify upper limit on packfile cache size and some cache entry expire policy.

'''Goal:''' Support for packfile cache in git-daemon,
            benchmark server load
'''Language:''' C

== Single credentials ==

Currently if you don't save your username and password in plain-text `.netrc` file (for HTTP transport), or avoid need for interactive credentials using public key / private key pair (for SSH), you need to repeat credentials many times during single git-fetch or git-clone command. The goal is to reuse existing connections if possible, so the whole transaction occurs using single connection and single credentials; if that is not possible cache credentials (in secure way) so user need to provide username and password at most once.

'''Goal:''' git-fetch and git-clone over HTTPS and git:// 
            requiring providing username and password at most once
'''Language:''' C (perhaps also shell script)

= Larger Projects =

== Directory renames ==

Git deals quite well with renames when merging. One of the corner cases is when one side renamed some directory, and other side created ''new files'' in the old-name directory. Git currently creates new files in resurrected old-name directory, while it could create new files under new-name directory instead.

There is a bit of controversy about this feature, as for example in some programming languages (e.g. Java) or in some project build tool info it is not posible to simply move a file (or create new file in different directory) without changing file contents. Some say that is better to fail than to do wrongly clean merge.

'''Goal:''' At minimum option enabling wholesame directory rename 
detection.  Preferred to add dealing with directory renames also to 
merge.  At last, one can try to implement "git log --follow" for 
directories.
'''Language:''' C
'''See:''' [http://thread.gmane.org/gmane.comp.version-control.git/99529 
|RFC PATCH v2 0/2| Detection of directory renames] thread on git 
mailing list (via GMane)
'''See also:'''
 * 
[http://thread.gmane.org/gmane.comp.version-control.git/80912/focus=81362 
merge renamed files/directories?] subthread on git mailing list
 * [http://thread.gmane.org/gmane.comp.version-control.git/108106 
Comments on "Understanding Version Control" by Eric S. Raymond] thread 
contains some thoughts on wholesame directory rename detection
 * [http://blog.teksol.info/2008/01/16/directory-renames-under-git 
Directory renames under Git] blog post notice the issue
 * [http://www.markshuttleworth.com/archives/123 Renaming is the killer 
app of distributed version control] blog post by Mak Shuttleworth 
(pro-Bazaar).