[Fedora-packaging] Reminder: GitHub etc. auto-generated archives are not stable in time

[Jan Pokorný]

Hello,

today, I've accidentally attested there are no stability guarantees
with the on-demand archives from common git hosting sites when preparing
a new pacemaker update, redownloading "spectool -s 0 pacemaker.spec"
of the original (-0.1.rc1, from 2 weeks ago) spec and comparing the
hashes, which (surprisingly to me) didn't match (they were at any similar
test in the past).  Then I looked at the adiff output:

>  diff -ru Unpack-2241/pacemaker-Pacemaker-1.1.17-rc1/configure.ac
> Unpack-6255/pacemaker-Pacemaker-1.1.17-rc1/configure.ac
>  --- Unpack-2241/pacemaker-Pacemaker-1.1.17-rc1/configure.ac2017-05-09 00:55:15.000000000
> +0200
>  +++ Unpack-6255/pacemaker-Pacemaker-1.1.17-rc1/configure.ac2017-05-09 00:55:15.000000000
> +0200
>  @@ -1159,7 +1159,7 @@
>   AC_PATH_PROGS(GIT, git false)
>   AC_MSG_CHECKING(build version)
>   
>  -BUILD_VERSION=0459f40
>  +BUILD_VERSION=0459f40958
>   if test  != ":%h$"; then
>      AC_MSG_RESULT(archive hash: ) 
 
for configure.ac that indeed has export-subst git attribute set
and the change itself arises from "$Format:%h$" substitution.
This likely means GitHub was internally updated to use equivalent
of git 2.11 feature of abbreviation length autoscaling within
last 14 days.

Hope this will be useful for some (e.g. fedora-review tool
has a check to redownload and diff sources against SRPM content,
IIRC).

-- 
Jan (Poki)