git compiled on same distro, different versions

git compiled on same distro, different versions

[Neal Kreitzinger]

If I only test a new git version (compiled from git.git source) on RHEL6 
before I put it on the RHEL5 box is that sufficient for validation?  Should 
git behave the same on both?  If not, why?

We don't have any RHEL5 VM images so it would be much easier for me to test 
on a RHEL6 VM.  I would have to justify the building of a RHEL5 image just 
for this purpose.

v/r,
neal 

Re: git compiled on same distro, different versions

[Junio C Hamano]

"Neal Kreitzinger" <neal@rsss.com> writes:

> If I only test a new git version (compiled from git.git source) on RHEL6 
> before I put it on the RHEL5 box is that sufficient for validation?  Should 
> git behave the same on both?  If not, why?

I somehow find this a strange question to ask to Git people; you may have
better luck asking the question to RHEL folks.

Having said that, one of the reasons the result may not work, off the top
of my head, is that the binary you compiled would expect to link with the
system libraries that are available on your RHEL6 installation.  If your
RHEL5 installation does not have a matching and ABI compatible library to
any of them, the resulting binary would obviously not work there.

Re: git compiled on same distro, different versions

[Neal Kreitzinger]

On 2/24/2012 4:08 PM, Junio C Hamano wrote:
> "Neal Kreitzinger"<neal@rsss.com>  writes:
>
>> If I only test a new git version (compiled from git.git source) on RHEL6
>> before I put it on the RHEL5 box is that sufficient for validation?  Should
>> git behave the same on both?  If not, why?
>
> I somehow find this a strange question to ask to Git people; you may have
> better luck asking the question to RHEL folks.
>
> Having said that, one of the reasons the result may not work, off the top
> of my head, is that the binary you compiled would expect to link with the
> system libraries that are available on your RHEL6 installation.  If your
> RHEL5 installation does not have a matching and ABI compatible library to
> any of them, the resulting binary would obviously not work there.
>
"high-level" question:
If I compile git 1.7.9.2 (from git.git source) on RHEL6 test-box and 
test it and conclude that it "works right" is that sufficient for me to 
then go ahead and compile git 1.7.9.2 on RHEL5 real-box and 
expect/assume that it will also "work right"?  IOW, will they produce 
the same results?  Because if not then I have just potentially broken 
the real-box.

"low-level" question:
I suspect git calls linux commands alot.  Git has "plumbing" commands 
that are not supposed to "break" scripts.  Does linux also have 
"plumbing" commands that are not supposed to "break" scripts?  Does git 
only use linux "plumbing" commands?  Because if git commands uses linux 
"porcelain" then the linux "porcelain" change could cause git to change 
(not necessarily "break").  Maybe git-porcelain only uses 
linux-porcelain, and git-plumbing only uses linux-plumbing.

Definitely thanks in advance for any replies!

v/r,
neal

Re: git compiled on same distro, different versions

[Holger Hellmuth]

On 25.02.2012 01:05, Neal Kreitzinger wrote:
> "high-level" question:
> If I compile git 1.7.9.2 (from git.git source) on RHEL6 test-box and
> test it and conclude that it "works right" is that sufficient for me to
> then go ahead and compile git 1.7.9.2 on RHEL5 real-box and
> expect/assume that it will also "work right"? IOW, will they produce the
> same results? Because if not then I have just potentially broken the
> real-box.

Depends on your thoroughness. I.e. you have to assume that your testing 
does actually test aspects that are not covered by all the tests 
included with git (and not detected by hundreds of other users on that 
platform). In that case you can't guarantee anything, even applying 
routine security patches to the operating system could potentially break 
things (and some companies really test every single patch they apply to 
mission-critical systems).

> "low-level" question:
> I suspect git calls linux commands alot. Git has "plumbing" commands
> that are not supposed to "break" scripts. Does linux also have
> "plumbing" commands that are not supposed to "break" scripts? Does git
> only use linux "plumbing" commands? Because if git commands uses linux
> "porcelain" then the linux "porcelain" change could cause git to change
> (not necessarily "break"). Maybe git-porcelain only uses
> linux-porcelain, and git-plumbing only uses linux-plumbing.

As far as I know there is no plumbing/porcelain distinction in the linux 
kernel. But while the internal interfaces in the kernel change a lot, 
the external interface (to user space programs like git) is relatively 
fixed. You can assume that git is adapted to incompatible changes very 
fast. But nobody can guarantee you that bugs won't make a difference 
going from one platform to another.