Re: Regression in git-subtree.sh, introduced in 2.20.1, after 315a84f9aa0e2e629b0680068646b0032518ebed

[Tom Clarkson <tqclarkson@icloud.com>]

> Is there a minimal, complete and verifiable example that other developers
> could use to analyze the bug?

I ran into this bug today, and while not much closer to a solution, I believe I understand why it is happening. 

The recursive search is required because the original rev-list based approach could leave out some relevant commits - ie reversion would replace an obvious bug with a hidden one.

The search will stop when it reaches either a root commit or one already mapped to a subtree commit.

If you have a small repo or run git subtree add directly on your master branch, the search will terminate fairly quickly.

However, if you do everything via pull requests, the search will hit a merge commit where one side is just ahead of the subtree mapping, but the other side is several thousand commits with no sign of either a root or any subtrees.

I’m not sure yet if it is the number of commits or merges specifically, but the script seems to be able to handle around 400-500 commits before it falls over.

>> 
>> 
>>> Am 09.12.2019 um 17:20 schrieb Johannes Schindelin <Johannes.Schindelin@gmx.de>:
>>> 
>>> Hi,
>>> 
>>>> On Mon, 9 Dec 2019, Marc Balmer wrote:
>>>> 
>>>> I am not familiar with the source code, so I can not send in that
>>>> revert.  I can, however, say that I am grateful to whomever does it ;)
>>> 
>>> I am against reverting the change without knowing the root cause.
>>> 
>>> The recent reporter only compared Git for Windows v2.19.0 vs v2.20.1,
>>> which is _quite_ a big difference.
>>> 
>>> For what I know, the problem might be a change in the MSYS2 runtime that
>>> is mistaken by some malware for malicious code (we did introduce some code
>>> to emulate Ctrl+C in MinTTY which injects a remote thread and executes
>>> ExitProcess() there, which might very well be construed as an attack, even
>>> if it is actually very much desired behavior).
>>> 
>>> These segmentation faults in `git subtree` on Windows have traditionally
>>> been _all_ because of overzealous anti-malware.
>>> 
>>> So first, a much more fine-grained analysis would be required, e.g.
>>> comparing v2.20.1 against v2.20.0, then copying _just_ the `git-subtree`
>>> file from a working into a non-working version (or vice versa; I would
>>> highly recommend using the portable versions for such side-by side
>>> comparison).
>>> 
>>> Ciao,
>>> Johannes
>>> 
>>>> 
>>>> - Marc
>>>> 
>>>> 
>>>>>> Am 09.12.2019 um 15:18 schrieb Strain, Roger L. <roger.strain@swri.org>:
>>>>> 
>>>>> As I said, I'm using a custom script here. I don't know if anybody else
>>>>> benefited from the change and hasn't said anything, but I won't object
>>>>> to someone submitting that revert.
>>>>> 
>>>>> --
>>>>> Roger
>>>>> 
>>>>> -----Original Message-----
>>>>> From: Marc Balmer <marc@msys.ch>
>>>>> To: "Strain, Roger L." <roger.strain@swri.org>
>>>>> Cc: ns@nadavsinai.com <ns@nadavsinai.com>, git@vger.kernel.org <
>>>>> git@vger.kernel.org>, Johannes.Schindelin@gmx.de <
>>>>> Johannes.Schindelin@gmx.de>, gitster@pobox.com <gitster@pobox.com>,
>>>>> pclouds@gmail.com <pclouds@gmail.com>
>>>>> Subject: Re: Regression in git-subtree.sh, introduced in 2.20.1, after
>>>>> 315a84f9aa0e2e629b0680068646b0032518ebed
>>>>> Date: Mon, 09 Dec 2019 15:13:47 +0100
>>>>> 
>>>>> Roger,
>>>>> 
>>>>> I am all for reverting it. if that does not cause any other regressions
>>>>> or headaches (or both...)
>>>>> 
>>>>> - Marc
>>>>> 
>>>>> 
>>>>> 
>>>>> Am 09.12.2019 um 15:11 schrieb Strain, Roger L. <roger.strain@swri.org>
>>>>> :
>>>>> 
>>>>> I haven't been able to find anything relating to the issue, but I also
>>>>> haven't had a repo that exposes the problem to test more thoroughly
>>>>> against. If this happens to be a public repo somewhere, I'd be more
>>>>> than happy to take a second look.
>>>>> 
>>>>> That being said, if the community feels it would be better to revert
>>>>> the changes that were introduced, I won't object. I've had to further
>>>>> customize the script for our internal use, and those changes aren't
>>>>> something that would be useful for the public at large. (A few changes
>>>>> relate to the presence/absence of a specific file, which I certainly
>>>>> wouldn't expect anyone else to have.) Short story is we're going to
>>>>> have to use a custom script going forward, so keeping or reverting the
>>>>> changes here make no difference to us. I still feel that the changes
>>>>> which were made make the script more correct, but clearly there's some
>>>>> undiagnosed logic error somewhere.
>>>>> 
>>>>> Honestly, I'm surprised we didn't see this particular issue show up on
>>>>> our own repo; it's ridiculously large and complex. At least if it had,
>>>>> I'd be able to troubleshoot it more reliably.
>>>>> 
>>>>> --
>>>>> Roger Strain
>>>>> 
>>>>> -----Original Message-----
>>>>> From: Nadav SInai <ns@nadavsinai.com>
>>>>> To: roger.strain@swri.org
>>>>> Cc: Johannes.Schindelin@gmx.de, git@vger.kernel.org, gitster@pobox.com,
>>>>> marc@msys.ch, pclouds@gmail.com
>>>>> Subject: RE: Regression in git-subtree.sh, introduced in 2.20.1, after
>>>>> 315a84f9aa0e2e629b0680068646b0032518ebed
>>>>> Date: Sun, 08 Dec 2019 12:30:48 +0200
>>>>> 
>>>>> [EXTERNAL EMAIL]
>>>>> 
>>>>> Hi, I'm curious if any of you had any luck in preventing that
>>>>> seg-fault in git-subtree script
>>>>> I'm encountering it myself using git 2.24.0.windows.2., seg-fault is
>>>>> in the same while loop (currently on line 757)
>>>>> When I tried your suggestion of adding the ($parents) ($rev) to the
>>>>> progress print I see that the last commit have only one revision
>>>>> printed
>>>>> like this:
>>>>> 
>>>>> 259/290 (523) [271] (843dd34090d36dfabd6a2e3e8459a4887427313b)
>>>>> (a69ee056f66acf66c63f89f55d26c0cc17036623)
>>>>> 259/290 (525) [273] (f5eea1a3cbe1e16acba53e8a9fe07b6525a8b97c)
>>>>> (843dd34090d36dfabd6a2e3e8459a4887427313b)
>>>>> 259/290 (527) [275] (82303752a428cf1d789ac9f156008adb2798b7b5)
>>>>> (f5eea1a3cbe1e16acba53e8a9fe07b6525a8b97c)
>>>>> 259/290 (528) [276]
>>>>> (7187897883c9fb4d33d4c87a02b876f8603728ff05f0945ae2ce9f98a35135)
>>>>> 259/290 (529) [277]
>>>>> (a00a3665343439a426671958dd90ed0407a22cad9ac9f156008adb2798b7b5)
>>>>> 259/290 (530) [278]
>>>>> (90beb94ebd331c457d79d05341453f5829a50bfcd4c87a02b876f8603728ff)
>>>>> 259/290 (531) [279]
>>>>> (9582e0acbed1910173564e250f350b5cc4291a7f671958dd90ed0407a22cad)
>>>>> 259/290 (532) [280]
>>>>> (f183930d6fabd3dccdddc5ec35d754ad28caf3b879d05341453f5829a50bfc)
>>>>> 259/290 (533) [281]
>>>>> (c9309f3a38c41f7991d9e78ddb47f7e85b8521eb564e250f350b5cc4291a7f)
>>>>> 259/290 (534) [282]
>>>>> (3bcf08f63a0e2b93ecc376bd679a16c80e99e7b1ddc5ec35d754ad28caf3b8)
>>>>> 259/290 (535) [283]
>>>>> (134621bb55a0470cdf6519ce08d6909af43ce0e5d9e78ddb47f7e85b8521eb)
>>>>> 259/290 (536) [284]
>>>>> (edb3471fbba29748f9784d29b3cee1dee2df4b37c376bd679a16c80e99e7b1)
>>>>> 259/290 (537) [285]
>>>>> (dd947a095df07a32dfd56666a395a7c42b25ca116519ce08d6909af43ce0e5)
>>>>> 259/290 (538) [286]
>>>>> (a639e09d2cbe1ea1149c080c1c95b8b018340ae2784d29b3cee1dee2df4b37)
>>>>> C:/Program Files/Git/mingw64/libexec/git-core\git-subtree: line 757:
>>>>> 8853 Done                    eval "$grl"
>>>>>   8854 Segmentation fault      (core dumped) | while read rev
>>>>> parents; do
>>>>> process_split_commit "$rev" "$parents" 0;
>>>>> done
>>>>> 
>>>>> I downgraded git to 2.19.0-windows.1 and it works now.
>>>>> 
>>>>> 
>>>>> I'm thankful for your insights
>>>>> Nadav Sinai
>>>>> Web Tech lead
>>>>> Philips-Algotec
>>>>> 
>>>>> 
>>>>> 
>>>>> 
>>>>> 
>>>> 
>>>> 
>> 
>>