Jeff King <peff@xxxxxxxx> wrote: > On Wed, Feb 10, 2021 at 09:55:43PM +0000, Eric Wong wrote: > > > This behavior of git-rev-parse is observed since git 1.8.3.1 > > at least(*), and likely earlier versions. > > > > At least one git-reliant project in-the-wild relies on this > > current behavior of git-rev-parse being able to handle multiple > > --since= arguments without squeezing identical results together. > > So add a test to prevent the potential for regression in > > downstream projects. > > I had to read this a few times to understand what "this behavior" meant. > It is just: when given multiple --since options, output a --max-age for > each of them, even though internally, Git's revision traversal will only > use one (in the usual last-one-wins fashion). > > I'm not sure if I was just being dense, or if this could be spelled out > more clearly. :) *shrug* :> My brain struggles with coherent thought so I'm surprised anybody is able to understand me at all :x > Out of curiosity, why does the other project want that? From your > mention of libgit2's git__date_parse(), I assume it's something that > wants to parse approxidates into timestamps in a script. Maybe we ought > to provide a more direct and robust way of doing that. We have a similar > need in t0006, but we use a test-helper program for it. It takes about 5ms for my system to run git-rev-parse once. I may be getting multiple approxidates at once, 1-2 in a typical input (start..end); but a strange or malicious input could have hundreds/thousands of approxidates to parse. Thus, I'm batching up all the approxidates into one rev-parse invocation (up to system argv limits right now). With the output lines split into an array, walking the output/input arrays in parallel will match them up. Hypothetically, if rev-parse were to get clever and deduplicate or reject identical inputs; then the parallel walk would be broken. > (I have no problem in the meantime with this patch, though; any new > method for accomplishing this would want to give other projects time to > adapt to its use). Yes. I think I've mentioned some years/decade ago having general functionality along the lines of "git cat-file --batch" or fast-import would be nice (even for some existing scripts and tests shipped with git). (v)fork+execve is painful even on Linux.
