Re: bootstrap/autogen.sh and git submodules

[Tim Rühsen]

On 03.03.19 19:03, Bruno Haible wrote:
> Hi,
> 
> When gnulib is used in a package, often the maintainers of that package
> use it via a git submodule, because that enables them to upgrade to newer
> versions of gnulib when they want to (and have a failsafe build between
> these upgrades), rather than having to adapt to gnulib changes at any moment.
> Even if it's only the imported file list which has changed, which might
> require an update to the package's .gitignore file.
> 
> The use of git submodules, however, has three problems:
> 
>   1) There are two use-cases of bootstrap/autogen.sh (the name does not 
> matter):
>        - first-time checkout and build of the sources,
>        - repeated build, possibly after modifying something in the submodule.
>      Currently bootstrap is optimized for the first one, and requires clumsy
>      recipes for the second one. Such as:
>        $ GNULIB_SRCDIR=`pwd`/gnulib ./autogen.sh --no-git
> 
>   2) A submodule has to be upgraded occasionally. bootstrap/autogen.sh does
>      not help doing this. I have to keep a command in a cheat-sheet:
>        $ (cd gnulib && git fetch && git merge origin/master); git add gnulib

You often see gnulib in a 'detached HEAD' state, so my variation is:
(cd gnulib && git checkout master && git pull): git commit -m "Update
gnulib" gnulib

>   3) As can be seen in the recent thread, there is considerable disagreement
>      regarding the handling of git submodules. Akim wants a fatal error when
>      some git submodules have not been initialized, whereas Tim hates this.

Not "hating" it, but it just fails ;-)
I was just searching for a way to disable the check... not sure what is
better suited, a cli option, an env variable or both.


> I would propose to split the common bootstrap or autogen.sh into two
> programs that can be invoked independently:
> 
>   1. A program that deals only with the git submodules.
>   2. A program that only generates files (or, regarding PO files, fetches
>      files that are not kept in git).
> 
> The developer should have the ability to set an environment variable
> (GNULIB_SRCDIR or GNULIB_TOOL), to be used by both programs.
> 
> Advantages:
>   - Developers can test modified gnulib sources without running through
>     hoops.
>   - Developers will have an easy way to upgrade to a newer gnulib version.
>   - Different project policies regarding submodules are isolated in one place
>     and thus have no influence on the gnulib-tool invocation, the PO file
>     handling, etc.
> 
> Disadvantages:
>   - The README-HACKING file will have to list two commands instead of one,
>     for the first-time checkout.
> 
> What's your opinion?

Make it so that existing build scripts don't have to be modified. E.g.
splitting bootstrap/autogen.sh into two commands is ok as long as the
original command invokes both (and thus being backwards compatible).

Regards, Tim

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