On Sat, Mar 25, 2017 at 8:15 PM, Daniel Ferreira (theiostream) <bnm...@gmail.com> wrote:
> SYNOPSIS > There are many advantages to converting parts of git that are still > scripts to C builtins, among which execution speed, improved > compatibility and code deduplication. agreed. > git-add--interactive, one of the most useful features of Git. knee jerk reaction: I never used it, so it cannot be that important ;) (I use git-gui, which is essentially the same workflow. There are tons of ways to accomplish a given goal using Git, so I guess we don't want to get in an argument here). > > FEASIBILITY > > There was only one discussion regarding the feasibility of its porting > (https://public-inbox.org/git/CAP8UFD2PcBsU6=FK4OHVrB7E98ycohS_0pYcbCBar=of1hl...@mail.gmail.com/). > It resulted in a consensus that doing it would be a task too large – > although interesting – for GSoC 2015 based on the amount of its lines > of code. It is, however, only a few lines larger than > git-rebase--interactive, which has been considered an appropriate > idea. As such, it looks like a possible project for three months of > full-time work. ok, it sounds a challenging project. (currently counting 1750 lines of code). Scrolling over the source code, there are quite a couple of functions, where the direct equivalent in C springs to mind. run_cmd_pipe -> see run-command.h unquote_path -> unquote_c_style ? refresh -> update_index_if_able() list_modified -> iterate over "const struct cache_entry *ce = active_cache[i];" > PROJECTED TIMELINE > - Prior to May 4 > -- Refine my basic knowledge of Perl > -- Craft one or two small patches to some of Git's Perl components > (preferentially to git-add--interactive itself) to improve my > understanding of the language and of how Git's Perl scripts actually > work > > - May 4 - May 30 > -- Clarify implementation details with my mentor, and work on a more > detailed roadmap for the project > -- Investigate roughly how to replace command invocations from the > script with actual builtin functions; which Git APIs in Perl already > have functional equivalents in C; which parts will require a full > rewrite. There are different approaches for replacing functionality in another language. Examples: * Implement the functionality in C and then have a "flag-day" commit 783d7e865e (builtin-am: remove redirection to git-am.sh, 2015-08-04) This only works when the whole functionality was replaced in prior commits * Implement partial functionality in C and call it via a helper function. 3604242f08 (submodule: port init from shell to C, 2016-04-15) This works well for only partial conversions (the larger the thing to convert the more appealing this is, as it gets code shipped early.) When choosing this strategy, this part of the Project would be to identify parts that could be ported on its own without much additional glue-code. > - May 30 - June 30 (start of coding period) > -- Define the architecture of the builtin within git (which > functions/interfaces will it have? where will its code reside?). > -- Implement a small subset of the builtin (to be defined with my > mentor) and glue it into the existing Perl script. Present this as a > first patch to get feedback early regarding the implementation and > avoid piling up mistakes early. > -- Do necessary changes based on this initial review. > -- Have roughly 1/3 of the script's functionality ported to C. > > - June 30 - July 28 > -- Port the remainder of the script to a builtin. > -- Have a weekly roadmap, sending a part of the patch every 15 days to > the mailing list for review and to avoid massive commits by the end of > GSoC. yeah; send early, send often. ;) > -- Apply suggestions from community reviews when possible; if not, > save them for doing toward the end of GSoC (see below). Please do not underestimate the discussion by community, finding consensus on list consumes a bit of time in some cases. > (Note: due to a previous commitment, during a five-day period of July > I will only be able to work part-time on GSoC. The actual week will be > known over the next weeks.) Maybe you want to shift the schedule up to here by one week then? (e.g. the first period would be April 27 - May 23) > > - July 28 - August 29 > -- By the start of this period, send a patch with the builtin fully > implemented to the mailing list. /a patch/a patch series consisting of many patches/ Experience shows that smaller patches are easier to review as it is more focused. Consider e.g. e86ab2c1cd (wt-status: convert to struct object_id, 2017-02-21) and the parents leading up to this commit. They work on the same big topic, but focus on very regional areas to ease review. > -- Fix bugs, test extensively, possibly extend test coverage for > git-add--interactive. AFAICT ('$ git grep "git add -i"') there is only t3701 testing the interactive add. Maybe we need to add tests first to document current behavior, before attempting a conversion? This could go well into the period "May 4 - May 30", as writing tests would count as "Clarify implementation details". Hope this helps, Stefan
