# [BUG] incorrect search result returned when using git log with a future date parameter 4 messages from 2013-01-30 to 2013-01-30. Participants: Caspar Zhang, Junio C Hamano, Jonathan Nieder. Thread: https://gitlist.dev/t/32774 ## Caspar Zhang, 2013-01-30 11:30 Subject: [BUG] incorrect search result returned when using git log with a future date parameter Message-ID: <51090466.9070105@casparzhang.com> URL: https://gitlist.dev/e/51090466.9070105%40casparzhang.com ``` Hi there, when I'm using the commit limit option `--before/--until` when doing `git log` search, I meet a bug when the upper-bound date is 10days later in the future. Here is an example: $ date +%F 2013-01-30 $ git log --oneline --since=2013-01-01 --until=2013-02-01 $ git log --oneline --since=2013-01-01 --until=2013-02-13 I debugged into the problem with ./test-date program in git source tree, got: $ ./test-date approxidate 2013-02-01 2013-02-01 -> 2013-02-01 10:47:13 +0000 // correctly parsed $ ./test-date approxidate 2013-02-13 2013-02-13 -> 2013-01-02 10:47:20 +0000 // incorrectly parsed When looking into the codes of date.c, in is_date() function, I found: 382 /* Be it commit time or author time, it does not make 383 * sense to specify timestamp way into the future. Make 384 * sure it is not later than ten days from now... 385 */ 386 if (now + 10*24*3600 < specified) 387 return 0; 388 tm->tm_mon = r->tm_mon; 389 tm->tm_mday = r->tm_mday; 390 if (year != -1) 391 tm->tm_year = r->tm_year; 392 return 1; If I comment Line 386 & 387 out, the parsing works correctly. So I guess here is the cause of the problem. Then I checked the git history, the change was introduced in commit 38035cf4 by Junio C Hamano (cc-ed): ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ commit 38035cf4a51c48cccf6c5e3977130261bc0c03a7 Author: Junio C Hamano Date: Wed Apr 5 15:31:12 2006 -0700 date parsing: be friendlier to our European friends. This does three things, only applies to cases where the user manually tries to override the author/commit time by environment variables, with non-ISO, non-2822 format date-string: - Refuses to use the interpretation to put the date in the future; recent kernel history has a commit made with 10/03/2006 which is recorded as October 3rd. - Adds '.' as the possible year-month-date separator. We learned from our European friends on the #git channel that dd.mm.yyyy is the norm there. - When the separator is '.', we prefer dd.mm.yyyy over mm.dd.yyyy; otherwise mm/dd/yy[yy] takes precedence over dd/mm/yy[yy]. Signed-off-by: Junio C Hamano ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ It seems like the original commit was going to fix European date style, but it fixed(?) the future date problem as well. However, this part of fix is not perfect: 1) it makes date parsing not working correctly. (see my test examples above). IMO, it should be in another place (maybe in commit.c or somewhere else?) we check if commit date is valid or not, instead of in the date parsing function. A date parsing function should parse _all dates with correctly format_, despite if it's an old date, or the date in the future. 2) from the test example I gave above, in fact the codes don't really prevent git from accepting the changes with illegal date, e.g., if there is a commit recorded as "2013-02-13", it will be parsed to "2013-01-02", which is a legal (old) date, thus, this commit will be accepted, but this is wrong. My suggestion is we might need to revert the first part of commit 38035cf4 since this part of code doesn't work correctly and causes problems; then we should create a new checking mechanism to prevent those "future date commits" to be accepted in other functions. I'm not able to do the second part since I'm not familiar with git codes yet.. :-( Thoughts? Caspar ``` ## Junio C Hamano, 2013-01-30 19:57 Subject: Re: [BUG] incorrect search result returned when using git log with a future date parameter Message-ID: <7vsj5ijvei.fsf@alter.siamese.dyndns.org> URL: https://gitlist.dev/e/7vsj5ijvei.fsf%40alter.siamese.dyndns.org In-Reply-To: <51090466.9070105@casparzhang.com> ``` Caspar Zhang writes: > .... A date parsing function should parse _all dates with > correctly format_, despite if it's an old date, or the date in the > future. When it is fed 2013-02-12, it is ambiguous and "approxidate" can and should use whatever heuristics (including rejection of future) to guess what the user wanted, but 2013-02-13 cannot be interpreted in any other way, so we should parse it as such. Patches welcome, as long as the fix does not make things worse for cases other than you observed. Thanks. ``` ## Jonathan Nieder, 2013-01-30 22:15 Subject: Re: [BUG] incorrect search result returned when using git log with a future date parameter Message-ID: <20130130221544.GA15680@google.com> URL: https://gitlist.dev/e/20130130221544.GA15680%40google.com In-Reply-To: <7vsj5ijvei.fsf@alter.siamese.dyndns.org> ``` Junio C Hamano wrote: > When it is fed 2013-02-12, it is ambiguous and "approxidate" can and > should use whatever heuristics (including rejection of future) to > guess what the user wanted, but 2013-02-13 cannot be interpreted in > any other way, so we should parse it as such. FWIW, if you said 02/12/2013, I'd agree, but I've never seen someone using 2013-02-12 to mean December 2. So that suggests another possible tweak on top. :) Thanks, Jonathan ``` ## Junio C Hamano, 2013-01-30 22:22 Subject: Re: [BUG] incorrect search result returned when using git log with a future date parameter Message-ID: <7v7gmujoqe.fsf@alter.siamese.dyndns.org> URL: https://gitlist.dev/e/7v7gmujoqe.fsf%40alter.siamese.dyndns.org In-Reply-To: <20130130221544.GA15680@google.com> ``` Jonathan Nieder writes: >> When it is fed 2013-02-12, it is ambiguous and "approxidate" can and >> should use whatever heuristics (including rejection of future) to >> guess what the user wanted, but 2013-02-13 cannot be interpreted in >> any other way, so we should parse it as such. > > FWIW, if you said 02/12/2013, I'd agree, but I've never seen someone > using 2013-02-12 to mean December 2. > > So that suggests another possible tweak on top. :) I think in the original context that triggered the "be more friendly to Europeans" discussion long time ago, some correlations between the delimiting characters (i.e. 'xxxx-xx-xx' vs 'xxxx.xx.xx' vs 'xxxx/xx/xx') and month-day ordering convention. I do not recall if we actually added that as a signal when disambiguating, though. ```