Making bash a formal requirement for build-infra?

[Magnus Ihse Bursie]

I was thinking of making bash a formal requirement for build-infra. In 
practice, this means that we should check if bash is present in 
configure, and fail directly otherwise.

Right now, I believe we have several "bash-isms" as it is already, but 
we try to execute with whatever shell we have, and we'll just get weird 
and hard-to-debug failures. The autoconf framework will, as it first 
action, go and look for bash, and run the generated configure script 
using bash, if that is available (regardless of what shell was used to 
start the configure script). Therefore we are unlikely to notice any 
bash-isms during development of build-infra.

I believe that we can count on bash being installed on all platforms we 
support, with the possible exception of Solaris systems -- I don't know 
how common it is to have bash there. On linux, cygwin and macosx I think 
it's ubiquitous.

If we choose *not* to require bash, then we really must start testing 
our scripts with other shells. Since autoconf will autodetect bash if 
present, that means setting up a machine where there is no bash 
installed (the horror! :-)).

If we conclude that we want to have bash as a formal requirement, that 
would mean that we can write much easier shell code, mostly in the 
configure script but possible also in the makefiles.

Any thoughts on this?

/Magnus