42b766d765
The break_delta_chain() function is recursive over the depth of a given delta chain, which can lead to possibly running out of stack space. Normally delta depth is quite small, but if there _is_ a pathological case, this is where we would find and fix it, so we should be more careful. We can do it without recursion at all, but there's a little bit of cleverness needed to do so. It's easiest to explain by covering the less-clever strategies first. The obvious thing to try is just keeping our own stack on the heap. Whenever we would recurse, push the new entry onto the stack and loop instead. But this gets tricky; when we see an ACTIVE entry, we need to care if we just pushed it (in which case it's a cycle) or if we just popped it (in which case we dealt with its bases, and no we need to clear the ACTIVE flag and compute its depth). You can hack around that in various ways, like keeping a "just pushed" flag, but the logic gets muddled. However, we can observe that we do all of our pushes first, and then all of our pops afterwards. In other words, we can do this in two passes. First dig down to the base, stopping when we see a cycle, and pushing each item onto our stack. Then pop the stack elements, clearing the ACTIVE flag and computing the depth for each. This works, and is reasonably elegant. However, why do we need the stack for the second pass? We can just walk the delta pointers again. There's one complication. Popping the stack went over our list in reverse, so we could compute the depth of each entry by incrementing the depth of its base, which we will have just computed. To go forward in the second pass, we have to compute the total depth on the way down, and then assign it as we go. This patch implements this final strategy, because it not only keeps the memory off the stack, but it eliminates it entirely. Credit for the cleverness in that approach goes to Michael Haggerty; bugs are mine. Signed-off-by: Jeff King <peff@peff.net> Signed-off-by: Junio C Hamano <gitster@pobox.com>
Git - fast, scalable, distributed revision control system
Git is a fast, scalable, distributed revision control system with an unusually rich command set that provides both high-level operations and full access to internals.
Git is an Open Source project covered by the GNU General Public License version 2 (some parts of it are under different licenses, compatible with the GPLv2). It was originally written by Linus Torvalds with help of a group of hackers around the net.
Please read the file INSTALL for installation instructions.
Many Git online resources are accessible from http://git-scm.com/ including full documentation and Git related tools.
See Documentation/gittutorial.txt to get started, then see
Documentation/giteveryday.txt for a useful minimum set of commands, and
Documentation/git-.txt for documentation of each command.
If git has been correctly installed, then the tutorial can also be
read with man gittutorial or git help tutorial, and the
documentation of each command with man git-<commandname> or git help <commandname>.
CVS users may also want to read Documentation/gitcvs-migration.txt
(man gitcvs-migration or git help cvs-migration if git is
installed).
The user discussion and development of Git take place on the Git mailing list -- everyone is welcome to post bug reports, feature requests, comments and patches to git@vger.kernel.org (read Documentation/SubmittingPatches for instructions on patch submission). To subscribe to the list, send an email with just "subscribe git" in the body to majordomo@vger.kernel.org. The mailing list archives are available at https://public-inbox.org/git, http://marc.info/?l=git and other archival sites.
The maintainer frequently sends the "What's cooking" reports that list the current status of various development topics to the mailing list. The discussion following them give a good reference for project status, development direction and remaining tasks.
The name "git" was given by Linus Torvalds when he wrote the very first version. He described the tool as "the stupid content tracker" and the name as (depending on your mood):
- random three-letter combination that is pronounceable, and not actually used by any common UNIX command. The fact that it is a mispronunciation of "get" may or may not be relevant.
- stupid. contemptible and despicable. simple. Take your pick from the dictionary of slang.
- "global information tracker": you're in a good mood, and it actually works for you. Angels sing, and a light suddenly fills the room.
- "goddamn idiotic truckload of sh*t": when it breaks