Re: [PATCH v4 2/2] git-version-gen: add --fallback option to use if git is not present

[Peter Rosin]

Hi Eric,

Thanks for the push!

On 2012-12-31 23:45, Eric Blake wrote:
> On 12/28/2012 03:13 PM, Peter Rosin wrote:
>> When building in a git checkout, but from a system lacking git, it
>> is useful to fall back to the version determined when the git
>> checkout was last used from a system sporting git.
>>
>> * build-aux/git-version-gen: Add support for the new option --fallback,
>> which comes into play when there is no $tarball_version_file and
>> git is not working.
> 
> You didn't really document how to wire up makefiles to properly inject a

I wanted to keep the patch small to evade the copyright assignment process
from stalling the changes.

> decent --fallback option into the script; but I'm at least satisfied
> that this patch in isolation doesn't break existing packages that don't
> use the --falback option, while leaving the door open for packages that
> DO want to support the use of --fallback.
> 
> As I understand it, the idea is that you have a shared folder that can
> be accessed via multiple machines; on some machines, you have git, and
> can therefore do a git checkout that populates Makefile with the right
> information for use as a fallback.  On other machines you lack git but
> can see the .git directory in the shared directory; since it is still a
> development build and you never ran 'make dist', you still want to have
> the effect of a devel checkout, rather than building from a tarball, and
> if all that git was needed for can be injected from the machine that has
> git installed, then the other machine can benefit from the --falback.

Right. (one nit though, it might be the same machine that accesses the
shared folder through different means, Cygwin vs MSYS in my case, where
Cygwin has git, but not MSYS)

> I just now noticed v5, so I'll check that out before pushing anything.

Good thing that.

> I will point out that your script introduces yet another instance of a
> non-portable construct:
> 
> test -z "$fallback"
> 
> Per the Autoconf manual:
> 
>      Posix also says that `test ! "STRING"', `test -n "STRING"' and
>      `test -z "STRING"' work with any string, but many shells (such as
>      Solaris, AIX 3.2, UNICOS 10.0.0.6, Digital Unix 4, etc.) get
>      confused if STRING looks like an operator:
> 
>           $ test -n =
>           test: argument expected
>           $ test ! -n
>           test: argument expected
>           $ test -z ")"; echo $?
>           0

Sigh...

> However, this idiom is already in use elsewhere in git-version-gen, so
> it should be fixed in an independent patch.

Thanks for tidying up!

And for the record, I have now fixed the Libtool "regression" using this
new support.

Cheers,
Peter