meaning of "Automatic date update in version.in" commits

[Mikhail Terekhov]

On 09/20/17 14:14, Matthias Klose wrote:
> On 20.09.2017 19:23, Petr Ovtchenkov wrote:
>> On Wed, 20 Sep 2017 18:16:45 +0200
>> Andreas Schwab <schwab@linux-m68k.org> wrote:
>>
>>> On Sep 20 2017, Petr Ovtchenkov <ptr@void-ptr.info> wrote:
>>>
>>>> What is the meaning of "Automatic date update in version.in" commits?
>>>> I mean commits like f625a739e5.
>>> It is used to name the shared libbfd and libopcodes, since there is no
>>> stable ABI.
>>>
>>>> This commits litter commits tree and create problems for  	
>>>> deterministic, bit-identical and/or verifiable builds.
>>> Why is that a problem?  The version is fixed for a particular source
>>> snapshot.
>>>
>> It's looks as a problem indeed:
>>     - garbage in commits
>>     - disorientation, when date present in SONAME
>>         0x000000000000000e (SONAME)             Library soname: [libbfd-2.29.0.20170729.so]
> this is correct, and it's usually set to not include the date for a releases, an
> exception being the 2.29.1 release, but things happen.
>
>> You see:
>>
>> git show 3110f4be18a2
>>    commit 3110f4be18a2f3b9fcd9663ed1dd141bbd6ed14f
>>    Author: GDB Administrator <gdbadmin@sourceware.org>
>>    Date:   Wed Sep 20 00:01:01 2017 +0000
>>
>>        Automatic date update in version.in
>>
>>    diff --git a/bfd/version.h b/bfd/version.h
>>    index 3405e42..955269f 100644
>>    --- a/bfd/version.h
>>    +++ b/bfd/version.h
>>    @@ -1,4 +1,4 @@
>>    -#define BFD_VERSION_DATE 20170919
>>    +#define BFD_VERSION_DATE 20170920
>>     #define BFD_VERSION @bfd_version@
>>     #define BFD_VERSION_STRING  @bfd_version_package@ @bfd_version_string@
>>     #define REPORT_BUGS_TO @report_bugs_to@
>>
>> git show f625a739
>>    commit f625a739e567f0110b2675539b7a0e5d5f67c5dc
>>    Author: GDB Administrator <gdbadmin@sourceware.org>
>>    Date:   Wed Sep 20 00:01:22 2017 +0000
>>
>>        Automatic date update in version.in
>>
>>    diff --git a/bfd/version.h b/bfd/version.h
>>    index 3405e42..955269f 100644
>>    --- a/bfd/version.h
>>    +++ b/bfd/version.h
>>    @@ -1,4 +1,4 @@
>>    -#define BFD_VERSION_DATE 20170919
>>    +#define BFD_VERSION_DATE 20170920
>>     #define BFD_VERSION @bfd_version@
>>     #define BFD_VERSION_STRING  @bfd_version_package@ @bfd_version_string@
>>     #define REPORT_BUGS_TO @report_bugs_to@
>>
>> git diff 3110f4be18a2 f625a739
>> ...
>> Ooops....
>>
>> This approch produce ambiguity, but try to conceal it.
> Feel free to limit the bumps to exactly one after another commit.
>
What if build scripts obtain date of last commit automatically i.e. 
something like this:

 Â Â Â  ~/tmp/gdb/binutils-gdb (master)>git log -1 --format=%cd 
--date=format:%Y%m%d
 Â Â Â  20170920

Then there is no need for additional commit.

Regards,
Mikhail