What: GIT - Fast Distributed Version Control System (DVCS)
Where: http://git-scm.com/
http://www.gitscm.org/
http://ozlabs.org/~paulus/gitk/
Description:
Git is popular version control system designed to handle
very large projects with speed and efficiency;
it is used mainly for various open source projects, most notably the Linux kernel.
Currently at version v1.6.5.2
Updated: 11/2009
Contact: See web siteIt is related to Tcl/Tk because there is gitk, a history visualization tool written in Tcl/Tk.
Branches in git are kind of like variables in Tcl. When one makes a commit, one creates a commit object, that "contains" the parent commit(s) and a directory tree specifying the current state of one's working directory, kind of like:
proc commit {} {
upvar #0 $::current_branch current
set current [list commit $::current_tree $current]
}(Rather than referencing things with pointers to Tcl_Objs however, things are referenced with 160-bit sha1 hashes.) Deleting a branch is like unsetting a variable: if that variable held the only reference to a particular value (commit), then the commit is gone too, but if anything else held another reference (e.g., it was merged into another branch, which results in a commit with more than one parent), then the commit is still there.
Of course, since all of it is stored on disk, it would be impractical to use a refcount scheme to reclaim unused memory. Instead git has a garbage collector git-gc. Until that is run, deleted commits (and whatever) can still be accessed by giving explicit hash numbers.
Zarutian 16. july 2007: Can git be obtained or compiled into a multiplatform starkit? Hard when one has only an thumbdrive/ipod to store stuff.
Lars H, 2008-06-05: Since it's a Unixy collection of many programs that do one thing each, I suspect this would be tricky (can't exec something in a vfs, can you?). Apparently there has been some work [L1 ] on turning it into a library, but that only got part of the way.
Makes me wonder, though… Could there be a semi-automatic way of turning a suite of C programs (like git, or at least the git plumbing) into a loadable extension which exposes each program as a Tcl command? (I expect one would have to do things like turning static C variables into fields of some dynamically allocated struct, to ensure reentrancy, but C is not my forte.)
FWIW, I later noticed that git has a concept of builtin command, with something rather close to a Tcl_CmdProc for every built-in subcommand of git. Probably not too hard to wrap manually, provided the built-in commands don't try to exec each other.
MAKR 2009-02-01: I updated the URLs as the main site apparently changed recently.
RJM 2010-10-05 added a page regarding an attempt to allow timestamp preservation of files: git timestamps
A thing that seems to be special about Git is that it tracks content (e.g. procedure definitions) rather than files (as CVS, SVN, and Mercurial does). See [L2 ].