Can't build when this repository is a git submodule

[alef]

Describe the bug

Your Makefile variable GIT_REFRESH_PREREQ relies on .git/index if path .git exists.
This doesn't apply to submodules because .git is a file here, instead of being a directory.
The error you get in such case:
make[1]: *** No rule to make target '.git/index', needed by 'version.inc'. Stop.

To Reproduce

Steps to reproduce the behavior (untested):

Kind of ...

$ mkdir /tmp/parent 
$ cd /tmp/parent
$ git init 
$ git submodule add https://github.com/cea-hpc/modules.git
$ cd modules
$ ./configure
$ make
...

Expected behavior

It should build even when you are a submodule of another git repository.

Additional context

Workaround: remove ".git/index".

[xdelaruelle]

Many thanks for this bug report. I have adapted tests of .git as it could be either a file or a directory. The git rev-parse --git-dir command is also now used to determine git directory location rather assuming it is .git.