Re: Bug Report: Subtrees and GPG Signed Commits

[Stephen R Guglielmo <srguglielmo@gmail.com>]

On Wed, Jan 31, 2018 at 7:33 AM, Stephen R Guglielmo
<srguglielmo@gmail.com> wrote:
> On Tue, Jan 30, 2018 at 6:37 PM, Avery Pennarun <apenwarr@gmail.com> wrote:
>> On Tue, Jan 30, 2018 at 6:24 PM, Junio C Hamano <gitster@pobox.com> wrote:
>>> Stefan Beller <sbeller@google.com> writes:
>>>> There has not been feedback for a while on this thread.
>>>> I think that is because subtrees are not in anyone's hot
>>>> interest area currently.
>>>>
>>>> This is definitely the right place to submit&discuss bugs.
>>>> Looking through "git log --format="%ae %s" -S subtree",
>>>> it seems as if Avery (apenwarr@gmail.com) was mostly
>>>> interested in developing subtrees, though I think he has
>>>> moved on. Originally it was invented by Junio, who is
>>>> the active maintainer of the project in 68faf68938
>>>> (A new merge stragety 'subtree'., 2007-02-15)
>>>
>>> Thanks for trying to help, but I have *NOTHING* to do with the "git
>>> subtree" subcommand (and I personally have no interest in it).  What
>>> I did was a subtree merge strategy (i.e. "git merge -s subtree"),
>>> which is totally a different thing.
>>>
>>> David Greene offered to take it over in 2015, and then we saw some
>>> activity by David Aguilar in 2016, but otherwise the subcommand from
>>> contrib/ has pretty much been dormant these days.
>>
>> Strictly speaking, the 'git subtree' command does in fact use 'git
>> merge -s subtree' under the covers, so Junio is at least partly
>> responsible for giving me the idea :)
>>
>> I actually have never looked into how signed commits work and although
>> I still use git-subtree occasionally (it hasn't needed any
>> maintenance, for my simple use cases), I have never used it with
>> signed commits.
>>
>> git-subtree maintains a cache that maps commit ids in the "original
>> project" with their equivalents in the "merged project."  If there's
>> something magic about how commit ids work with signed commits, I could
>> imagine that causing the "no a valid object name" problems.  Or,
>> git-subtree in --squash mode actually generates new commit objects
>> using some magic of its own.  If it were to accidentally copy a
>> signature into a commit that no longer matches the original, I imagine
>> that new object might get rejected.
>>
>> Unfortunately I don't have time to look into it.  The git-subtree code
>> is pretty straightforward, though, so if Stephen has an hour or two to
>> look deeper it's probably possible to fix it up.  The tool is not
>> actually as magical and difficult as it might seem at first glance :)
>>
>> Sorry I can't help more.
>>
>> Good luck,
>>
>> Avery
>
> Thanks all for the discussion/replies.
>
> We use subtrees extensively in our environment right now. The "sub"
> repos (90+) are located on GitHub, while the "main/parent" repo is
> provided by a vendor on website hosting infrastructure.
>
> I will take a look at:
> git/Documentation/CodingGuidelines
> git/Documentation/SubmittingPatches
> git/contrib/subtree/
>
> Should I follow up in this thread with a patch (it might be a while)?
>
> Thanks!
> Steve

Hi all,

It looks like I've found the cause of the issue. I have
log.showsignature=true in my gitconfig. The toptree_for_commit()
function calls `git log` and passes the output to `git commit-tree` in
new_squash_commit(). Apparently commit-tree doesn't like GPG sigs.

The fix was simple: --no-show-signature. However, I believe this was
added in git v2.10.0, so it's not fully backwards compatible. I'm open
to suggestions on a better fix if this is not acceptable.

Thanks!


https://github.com/srguglielmo/git/commit/822c8a45d049f86ea5c59c0b434303964e4e6f3d



diff --git a/contrib/subtree/git-subtree.sh b/contrib/subtree/git-subtree.sh
index cc033af73..dec085a23 100755
--- a/contrib/subtree/git-subtree.sh
+++ b/contrib/subtree/git-subtree.sh
@@ -475,7 +475,7 @@ squash_msg () {

 toptree_for_commit () {
        commit="$1"
-       git log -1 --pretty=format:'%T' "$commit" -- || exit $?
+       git log --no-show-signature -1 --pretty=format:'%T' "$commit"
-- || exit $?
 }

 subtree_for_commit () {